There are 15 places wherein the opinion of Umar (Radhiallaahu Anhu) conformed to revelation.

There are nine instances in which verses were revealed exactly as Hadhrat Umar (Radhiallaahu Anhu) had suggested.

1. Maqaam Ibraahim: wherein Umar (Radhiallaahu Anhu) told Nabi (Sallallaahu Alayhi Wasallam), “Why don’t you make the Maqaam Ibraahim (Alayhis salaam) a prayer place?” Allah revealed the Aayat, “And the Maqaam of Ibrahim (Alayhis salaam) a prayer place.” (Baqarah 124)
2. Hijaab: Hadhrat Aaisha (Radhiallaahu Anha) said that after the laws of Hijaab were implemented, Hadhrat Sawda (Radhiallaahu Anha) went out for some need. Despite being covered, she could still be recognised. Hence, Umar (Radhiallaahu Anhu) recognised her and said, “O Sawda, look at how you have come out, by Allah you cannot hide.” Sawda (Radhiallaahu Anha) immediately went to Rasulullah (Sallallaahu Alayhi Wasallam) who was eating at the house of Aaisha (Radhiallaahu Anha). Nabi (Sallallaahu Alayhi Wasallam) had a bone in his hand. Sawda (Radhiallaahu Anha) told Nabi (Sallallaahu Alayhi Wasallam) that she had went out for some need and Umar (Radhiallaahu Anhu) told her such and such. Hadhrat Aaisha (Radhiallaahu Anha) narrates that the bone was still in the hand of Rasulullah (Sallallaahu Alayhi Wasallam) and he hadn’t yet placed it when Wahy (revelation) came to Rasulullah (Sallallaahu Alayhi Wasallam). After the revelation was complete, Nabi (Sallallaahu Alayhi Wasallam) told the women that they have been given permission to go out for need only if they are properly covered. (Mazaahirul Haqq vol.9 pg.430)
3. Prisoners of Badr: Nabi (Sallallaahu Alayhi Wasallam) made Mashwara with the Sahaaba (Radhiallaahu Anhum) regarding the prisoners. Umar (Radhiallaahu Anhu) said, “O Rasulullah (Sallallaahu Alayhi Wasallam), these Kuffaar should be killed by chopping their necks.” Nabi (Sallallaahu Alayhi Wasallam) accepted the opinion of Abu Bakr (Radhiallaahu Anhu) to free them and take a ransom. The Aayaat, “It is not for a prophet that he have prisoners of war…” (Anfaal 67) was revealed.
4. Umar (Radhiallaahu Anhu) told the wives of Rasulullah (Sallallaahu Alayhi Wasallam), “Either you will refrain from displeasing Rasulullah (Sallallaahu Alayhi Wasallam) or Allah Ta’ala will replace you with wives who will be better than you…” Then a similar Aayaat was revealed, “It may be if he divorced you that his Lord will grant him instead of you, wives better than you.” (Al-Tahrim 5)
5. When Nabi (Sallallaahu Alayhi Wasallam) separated from his wives in an enclosure, Umar (Radhiallaahu Anhu) told Nabi (Sallallaahu Alayhi Wasallam), “If you divorce your wives, then Allah Ta’ala and Jibraaeel (Alayhis salaam) and myself and Abu-bakr and the believers are with you.” Then Allah Ta’ala revealed a similar Aayat, “but if you help one another against him (Muhammad), then verily Allah is his Mawla (Lord) and Jibraaeel and the righteous among believers and angels are his helpers…” (Al-Tahrim 4)
6. When Abdullah ibn Ubayy (a Munaafiq) passed away, then Nabi (Sallallaahu Alayhi Wasallam) wanted to perform his Janaaza Salaat. Umar (Radhiallaahu Anhu) held the clothes of Nabi (Sallallaahu Alayhi Wasallam) and prevented him from doing so. Allah Ta’ala revealed, “And never (O Muhammad) pray (funeral prayer) for any of them (hypocrites) who dies.” (Tawbah 84)
7. When the Aayat, “Even if you ask forgiveness for them 70 times, Allah will not forgive them.” (Tawbah 80). Nabi (Sallallaahu Alayhi Wasallam) said, “Definitely, I will increase upon 70” and he began making Istighfaar for them. Then Umar (Radhiallaahu Anhu) said, “O Rasulullah (Sallallaahu Alayhi Wasallam), Allah will not forgive them at all whether you make Istighfaar for them or not.” Then, the Aayat, “It is equal to them whether you (Muhmmad) ask for forgiveness or ask not forgiveness for them. Allah will never forgive them.” (Munaafiqoon 6)
8. When the Aayat, “And We created man (Adam) out of an extract of clay. Thereafter, We made him as a Nutfah…” (Surah Mu’minoon 12-14) came, Umar (Radhiallaahu Anhu) remarked, “Glory be to Allah, the best of all creators.” The same Aayat was revealed. According to some narrations, Nabi (Sallallaahu Alayhi Wasallam) exclaimed, “Are you increasing on the Qur’aan, O Umar?” Thereafter, Jibraaeel (Alayhis salaam) descended with revelation and said to Nabi (Sallallaahu Alayhi Wasallam) that is the completion of those Aayaats.
9. When Nabi (Sallallaahu Alayhi Wasallam) made Mashwara with the Sahaaba (Radhiallaahu Anhum) regarding Aaisha (Radhiallaahu Anha) when the incident of Ifk (accusation of Zina took place), Umar (Radhiallaahu Anhu) asked Nabi (Sallallaahu Alayhi Wasallam), “Who has made your Nikah to her O Rasulullah (Sallallaahu Alayhi Wasallam)?” Nabi (Sallallaahu Alayhi Wasallam) replied, “Allah Ta’ala.” Umar (Radhiallaahu Anhu) said, “Do you think that your Lord deceived you on that? Glory be to You (Allah), this is a great lie.” (Noor 16) Then Allah Ta’ala revealed the exact same words.

There are four Aayats revealed which were similar to the opinion offered by Hadhrat Umar (Radhiallaahu Anhu).

The Aayaats were not exactly like the opinions of Hadhrat Umar (Radhiallaahu Anhu) as in the previous nine Aayaats.

1. Umar (Radhiallaahu Anhu) said to the Jews: “I implore you in the name of Allah! Do you find the description of Muhammad (Sallallaahu Alayhi Wasallam) in your books?” They replied, “Yes.” He then asked them, “What is stopping you from following him?” They said, “Verily Allah does not send a messenger except that there is an angel appointed for him. Verily, Jibraaeel (Alayhis salaam) is the one who has been appointed for Muhammad (Sallallaahu Alayhi Wasallam) and he is our enemy from the angels, and Mikaaeel is our friend. If he had been with Nabi (Sallallaahu Alayhi Wasallam), we would have followed him.” Umar (Radhiallaahu Anhu) then told them, “Verily, I bear witness that Mikaaeeel does not have animosity for the friends of Jibraaeel (Alayhis salaam) and Jibraaeel (Alayhis salaam) does not befriend the enemies of Mikaaeel (Alayhis salaam).” The Aayat, “Say (O Muhammad), whoever is an enemy to Jibraaeel (Alayhis salaam) (let him die in his fury), for indeed he has brought it (Qur’aan) down to your heart by Allah’s permission confirming what came before it and (offers) guidance and glad tidings for the believers. Whoever is an enemy to Allah, His angels, His messengers, Jibraaeel and Mikaaeel, then verily Allah is an enemy to the disbelievers.” (Baqarah 98)
2. Umar (Radhiallaahu Anhu) was desperate for wine to become Haraam and he used to say, “O Allah explain for us regarding wine, because verily it destroys wealth and intelligence.” Then the Aayat, “They ask you (Muhammad) about wine and gambling; say, in them is a great sin and some benefit, but the sin is greater than their benefit.” (Baqarah 219). Nabi (Sallallaahu Alayhi Wasallam) recited this Aayat to Umar (Radhiallaahu Anhu), but he did not find clarity; hence, he said, “O Allah, explain to us clearly.” Then the Aayat, “O you who believe, do not come close to Salaat whilst you are intoxicated.” (Nisaa 43). Nabi (Sallallaahu Alayhi Wasallam) read this Aayat to him, but he did not find proper clarity still so he said, “O Allah explain to us regarding wine very clearly.” Then the Aayat, “O you who believe, intoxicants and gambling … are an abomination of Shaytaan… so avoid it.” (Maaidah 90). Nabi (Sallallaahu Alayhi Wasallam) read this to Umar (Radhiallaahu Anhu). Then Umar (Radhiallaahu Anhu) finally stated, “We have stopped, O our Lord, we have stopped.”
3. Abdullah ibn Abbaas (Radhiallaahu Anhu) narrates that once Nabi (Sallallaahu Alayhi Wasallam) sent a person from the Ansaar to Umar (Radhiallaahu Anhu) during the afternoon to call him. When he came to Umar (Radhiallaahu Anhu), he found Umar in such a condition that Umar disliked anybody seeing him. Umar (Radhiallaahu Anhu) then said, “O Rasulullah (Sallallaahu Alayhi Wasallam), I hope Allah Ta’ala commands us and directs us regarding the aspect of seeking permission.” Thereafter the Aayat, “O you who believe, let your slaves and those among you who have not come to the age of puberty ask permission (before coming to your presence) on three occasions: before Fajr, while you put off your clothes for noonday rest…” (Noor 58)
4. When the Aayat, “(in the gardens of delight) a multitude of those will be from the first generation. And a few from later generation.” (Waaqiah 13) was revealed, Umar (Radhiallaahu Anhu) began to cry and said, “O Rasulullah (Sallallaahu Alayhi Wasallam) and little from the later generations. We believe in the messenger of Allah and testify in him and which little from us will be saved?” Then Allah Ta’ala revealed the Aayat, “A multitude will be from the first generations and a multitude from the later generations.” (Waaqiah 39-40). Nabi (Sallallaahu Alayhi Wasallam) then called him and told him that Allah Ta’ala has revealed what you said.

There were two opinions of Hadhrat Umar (Radhiallaahu Anhu) which the Jews confirmed to be in the Tawrah.

1. Tariq ibn Shihaab (Radhiallaahu Anhu) narrates that a Jew came to Umar (Radhiallaahu Anhu) and asked him, “Do you see the Aayat of Allah in the Qur’aan? ‘and hasten to forgiveness from your Lord and a Jannat whose width is the skies and earth. It is prepared for the muttaqeen (God-fearing).’ (Aali Imraan 133)

“In that case, where is the fire, i.e. Jahannum?” Umar (Radhiallaahu Anhu) told the other Sahaaba (Radhiallaahu Anhu) that were present to answer him, but none of them could answer. Umar (Radhiallaahu Anhu) then said to him, “Do you notice the day when it comes, doesn’t it fill the skies and earth?” He replied, “Yes, indeed.” Umar (Radhiallaahu Anhu) then asked him, “Then where is the night?” he replied, “to wherever Allah Ta’ala wishes.” Umar (Radhiallaahu Anhu) then told him (in the same way) “the fire is also wherever he wishes it to be.” The Jew then took an oath saying to Umar (Radhiallaahu Anhu) that, “O Ameerul Mu’mineen, verily it has been revealed in the book of Allah in the same way.”

2. It has been narrated that Ka’ab Ahbaar (a famous Jewish rabbi) once said to Umar, “Destruction to the king of the world from the King of the sky.” Umar (Radhiallaahu Anhu) said, “with the exception of that person who restrains himself.” Ka’ab then said, “By oath on that being in whose hands is my life, verily I have found it in the book of Allah.” Umar (Radhiallaahu Anhu) then fell into Sajdah for Allah.

(Irshaad-us-saari vol.10 pg.518; Ilmiyyah)

and Allah Ta’ala Knows Best

Source: https://islambestreligion.wordpress.com/2012/09/01/hazrat-umar-ra-the-quran-revelation/