Hadith: there is a verse in your Book; had it been sent down to us, the community of Jews, we would have taken this day as a festival

عَنْ عُمَرَ بْنِ الخَطَّابِ رَضِيَ اللَّهُ عَنْهُ:
أَنَّ رَجُلًا مِنَ اليَهُودِ قَالَ لَهُ: يَا أَمِيرَ المُؤْمِنِينَ، آيَةٌ فِي كِتَابِكُمْ تَقْرَؤُونَهَا، لَوْ عَلَيْنَا مَعْشَرَ اليَهُودِ نَزَلَتْ لاَتَّخَذْنَا ذَلِكَ اليَوْمَ عِيدًا، قَالَ: أَيُّ آيَةٍ؟ قَالَ: {اليَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الإِسْلاَمَ دِينًا} [المائدة: 3] قَالَ عُمَرُ: قَدْ عَرَفْنَا ذَلِكَ اليَوْمَ، وَالمَكَانَ الَّذِي نَزَلَتْ فِيهِ عَلَى النَّبِيِّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، وَهُوَ قَائِمٌ بِعَرَفَةَ يَوْمَ جُمُعَةٍ.
[صحيح] - [متفق عليه] - [صحيح البخاري: 45]

‘Umar ibn al-Khattāb (may Allah be pleased with him) reported:
A man from the Jews said to him: O Commander of the Believers, there is a verse in your Book; had it been sent down to us, the community of Jews, we would have taken this day as a festival. He said: Which verse? He said: {Today I have perfected your religion for you, completed My favor upon you, and have chosen Islam as your religion.} [Surat al-Mā’idah: 3]. ‘Umar said: Indeed, we know that day and the place where it was revealed to the Prophet (ﷺ) while he was standing at ‘Arafah on a Friday.
[Authentic hadith] - [Narrated by Bukhari & Muslim] - [Sahih Bukhari - 45]

Explanation

A man from among the Jews came to the Commander of the Believers, ‘Umar ibn al-Khattāb (may Allah be pleased with him), and said: There is a verse in your Book—the Qur’an—which you recite. If it had been revealed to us, the Jews, in our Book, the Torah, we would have taken that day as a festival, celebrating it in gratitude for the blessing of such a great verse. ‘Umar (may Allah be pleased with him) asked: Which verse is that? He said: {Today I have perfected your religion for you, completed My favor upon you, and have chosen Islam as your religion.} ‘Umar (may Allah be pleased with him) replied: We know well the day and the place in which this noble verse was revealed. It was sent down on a day of celebration—on Friday—while the Prophet (ﷺ) was standing at ‘Arafah. Both are great days for the Muslims.

Benefits from the Hadith

1. This shows ‘Umar's great care and attention to both the place and the time where the verse was revealed.
2. This verse highlights the immense favor that Allah Almighty has bestowed upon this Ummah, as He perfected their religion and completed His blessings upon them so that they are in no need of any addition in religion. Therefore, anything introduced into the religion after its completion—without evidence from it—is considered an innovation and a misguidance, as it was authentically reported from the Prophet (ﷺ) that he said: "Whoever introduces into this matter of ours that which is not part of it, it will be rejected."
3. This Hadīth indicates that festivals are not to be established based on personal opinion or innovation, as was done by the People of the Book before us. Rather, they are determined by divine law and prophetic guidance. This verse, which declares the perfection of the religion and the completion of Allah's favor, was revealed on a day that Allah Himself ordained as a festival for this Ummah in two respects: First, it was revealed on Friday, which is the weekly festival for Muslims; and second, it coincided with the Day of ‘Arafah, which is the festival of the pilgrims, their greatest gathering, and their most significant occasion.
4. As-Sa‘di said in his commentary on this verse: {Today I have perfected your religion for you} by completing the victory of Islam and perfecting both its outward and inward laws, its fundamentals and its branches. For this reason, the Qur’an and the Sunnah are entirely sufficient in addressing all matters of religion, both its principles and its subsidiary issues. Therefore, anyone who claims that people must rely on other sciences besides the Qur’an and Sunnah to understand their beliefs and rulings—such as speculative theology and the like—is ignorant and false in his claim. Such a person implies that the religion is incomplete without what he has introduced, and this is among the gravest forms of injustice and ignorance toward Allah and His Messenger. {Completed My favor upon you} both the outward and inward; {and have chosen Islam as your religion} i.e., I have chosen and selected it for you as your way of life, just as I have chosen you for it. So uphold it in gratitude to your Lord, and praise the One Who has blessed you with the noblest, most complete, and most perfect of religions.