Sunan an-Nasa'i, Volume 3, Book 21, Hadith 2040 (DarusSalam) ⓘ

It was narrated that 'Alqamah bin Abi 'Alqamah, from his mother, that she heard 'Aishah say: "The Messenger of Allah got up one night and got dressed, then he went out. I told my slave girl Barirah to follow him, so she followed him until he came to Al-Baqi. Then he stood near if for as long as Allah willed that he should stand, then he left. Barirah came back before he did and told me, but I did not mention anything until morning came, then I mentioned that to him. He said: 'I was sent to the people of Al-Baqi' to pray for them."'

أَخْبَرَنِي مُحَمَّدُ بْنُ سَلَمَةَ، وَالْحَارِثُ بْنُ مِسْكِينٍ، قِرَاءَةً عَلَيْهِ وَأَنَا أَسْمَعُ، - وَاللَّفْظُ لَهُ - عَنِ ابْنِ الْقَاسِمِ، قَالَ حَدَّثَنِي مَالِكٌ، عَنْ عَلْقَمَةَ بْنِ أَبِي عَلْقَمَةَ، عَنْ أُمِّهِ، أَنَّهَا سَمِعَتْ عَائِشَةَ، تَقُولُ ‏:‏ قَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم ذَاتَ لَيْلَةٍ فَلَبِسَ ثِيَابَهُ ثُمَّ خَرَجَ - قَالَتْ - فَأَمَرْتُ جَارِيَتِي بَرِيرَةَ تَتْبَعُهُ فَتَبِعَتْهُ حَتَّى جَاءَ الْبَقِيعَ، فَوَقَفَ فِي أَدْنَاهُ مَا شَاءَ اللَّهُ أَنْ يَقِفَ، ثُمَّ انْصَرَفَ فَسَبَقَتْهُ بَرِيرَةُ فَأَخْبَرَتْنِي، فَلَمْ أَذْكُرْ لَهُ شَيْئًا حَتَّى أَصْبَحْتُ، ثُمَّ ذَكَرْتُ ذَلِكَ لَهُ فَقَالَ ‏:‏ ‏ "‏ إِنِّي بُعِثْتُ إِلَى أَهْلِ الْبَقِيعِ لأُصَلِّيَ عَلَيْهِمْ ‏" ‏ ‏.‏