ENOfficial
Narrated 'Umar (RA): He said: I said: O Allah's Messenger (ﷺ), I made a vow in the Jahiliyya times to spend a night in devotion (I'tikaf) in the Sacred Mosque. He (the Prophet) said, "Fulfill your vow." . al-Bukhari added in another narration: "Then, spend a night in devotion (in the Sacred Mosque)."
Source: sunnah.com
Other translations
Arabic
وَعَنْ عُمَرَ - رضى الله عنه - قَالَ: { قُلْتُ: يَا رَسُولَ اَللَّهِ! إِنِّي نَذَرْتُ فِي اَلْجَاهِلِيَّةِ; أَنْ أَعْتَكِفَ لَيْلَةً فِي اَلْمَسْجِدِ اَلْحَرَامِ. قَالَ: "فَأَوْفِ بِنَذْرِكَ" } مُتَّفَقٌ عَلَيْهِ 1 وَزَادَ اَلْبُخَارِيُّ فِي رِوَايَةٍ 2 { فَاعْتَكَفَ لَيْلَةً } 3 .
sunnah.com