Messenger of Allah, I had taken a vow during the days of Ignorance (Jahiliyya) that I would observe I'tikaf for a night in the Sacred Mosque. He (the Holy Prophet) said: Fulfil your vow.  

يَا رَسُولَ اللَّهِ إِنِّي نَذَرْتُ فِي الْجَاهِلِيَّةِ أَنْ أَعْتَكِفَ لَيْلَةً فِي الْمَسْجِدِ الْحَرَامِ قَالَ فَأَوْفِ بِنَذْرِكَ  

This hadith is transmitted on the authority of Ibn Umar with a slight variation of words.  

عَنْ عُمَرَ بِهَذَا الْحَدِيثِ أَمَّا أَبُو أُسَامَةَ وَالثَّقَفِيُّ فَفِي حَدِيثِهِمَا اعْتِكَافُ لَيْلَةٍ وَأَمَّا فِي حَدِيثِ شُعْبَةَ فَقَالَ جَعَلَ عَلَيْهِ يَوْمًا يَعْتَكِفُهُ وَلَيْسَ فِي حَدِيثِ حَفْصٍ ذِكْرُ يَوْمٍ وَلاَ لَيْلَةٍ  

Messenger of Allah, I had taken a vow during the days of Ignorance that I would observe I'tikaf for one day in the Sacred Mosque. So what is your opinion? He said: Go and observe I'tikaf for a day. And Messenger of Allah ﷺ gave him a slave girl out of the one-fifth (of the spoils of war meant for the Holy Prophet). And when Messenger of Allah (inay peace be upon him) set the war prisoners free. 'Umar b. Khattab heard their voice as they were saying: Messenger of Allah ﷺ has set as free. He (Hadrat 'Umar) said: What is this? They said: Messenger of Allah ﷺ has set free the prisoners of war (which had fallen to the lot of people). Thereupon he (Hadrat 'Umar) said: Abdullah, go to that slave-girl and set her free.  

أَنَّ عُمَرَ بْنَ الْخَطَّابِ سَأَلَ رَسُولَ اللَّهِ ﷺ وَهُوَ بِالْجِعْرَانَةِ بَعْدَ أَنْ رَجَعَ مِنَ الطَّائِفِ فَقَالَ يَا رَسُولَ اللَّهِ إِنِّي نَذَرْتُ فِي الْجَاهِلِيَّةِ أَنْ أَعْتَكِفَ يَوْمًا فِي الْمَسْجِدِ الْحَرَامِ فَكَيْفَ تَرَى قَالَ اذْهَبْ فَاعْتَكِفْ يَوْمًا قَالَ وَكَانَ رَسُولُ اللَّهِ ﷺ قَدْ أَعْطَاهُ جَارِيَةً مِنَ الْخُمْسِ فَلَمَّا أَعْتَقَ رَسُولُ اللَّهِ ﷺ سَبَايَا النَّاسِ سَمِعَ عُمَرُ بْنُ الْخَطَّابِ أَصْوَاتَهُمْ يَقُولُونَ أَعْتَقَنَا رَسُولُ اللَّهِ ﷺ فَقَالَ مَا هَذَا فَقَالُوا أَعْتَقَ رَسُولُ اللَّهِ ﷺ سَبَايَا النَّاسِ فَقَالَ عُمَرُ يَا عَبْدَ اللَّهِ اذْهَبْ إِلَى تِلْكَ الْجَارِيَةِ فَخَلِّ سَبِيلَهَا  

When Allah's Apostle ﷺ came back from the Battle of Hunain, Umar asked Messenger of Allah ﷺ about the vow he had taken during the days of Ignorance that he would observe I'tikaf for a day. The rest of the hadith is the same.  

لَمَّا قَفَلَ النَّبِيُّ ﷺ مِنْ حُنَيْنٍ سَأَلَ عُمَرُ رَسُولَ اللَّهِ ﷺ عَنْ نَذْرٍ كَانَ نَذَرَهُ فِي الْجَاهِلِيَّةِ اعْتِكَافِ يَوْمٍ ثُمَّ ذَكَرَ بِمَعْنَى حَدِيثِ جَرِيرِ بْنِ حَازِمٍ  

A mention of Messenger of Allah ﷺ observing 'Umra from ja'rina was made before Ibn 'Umar. He said: He did not enter into the state of Ihram from that (place), and Umar had taken a vow of observing I'tikaf for a night during the days of Ignorance. The rest of the hadith is the same.  

ذُكِرَ عِنْدَ ابْنِ عُمَرَ عُمْرَةُ رَسُولِ اللَّهِ ﷺ مِنَ الْجِعْرَانَةِ فَقَالَ لَمْ يَعْتَمِرْ مِنْهَا قَالَ وَكَانَ عُمَرُ نَذَرَ اعْتِكَافَ لَيْلَةٍ فِي الْجَاهِلِيَّةِ ثُمَّ ذَكَرَ نَحْوَ حَدِيثِ جَرِيرِ بْنِ حَازِمٍ وَمَعْمَرٍ عَنْ أَيُّوبَ  

This hadith has been transmitted on the authority of Ibn Umar through another chain of transmitters but with a slight variation of words.  

عَنِ ابْنِ عُمَرَ بِهَذَا الْحَدِيثِ فِي النَّذْرِ وَفِي حَدِيثِهِمَا جَمِيعًا اعْتِكَافُ يَوْمٍ