Musnad Ahmad 39
It was narrated that Ibn 'Abbas said:
When they wanted to dig a grave for the Messenger of Allah (ﷺ), Abu 'Ubaidah bin al-Jarrah used to dig graves in the manner of the people of Makkah and Abu Talhah Zaid bin Sahl used to dig graves for the people of Madinah, and he would make a niche in the side of the grave. Al-'Abbas called two men and said to one of them, Go to Abu ‘Ubaidah; and to the other he said, Go to Abu Talhah. O Allah, choose for Your Messenger. The one who had been sent to Abu Talhah found him, so he came and dug a grave with a niche in its side for the Messenger of Allah (ﷺ).
حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا أَبِي، عَنِ ابْنِ إِسْحَاقَ، قَالَ وَحَدَّثَنِي حُسَيْنُ بْنُ عَبْدِ اللَّهِ، عَنْ عِكْرِمَةَ، مَوْلَى ابْنِ عَبَّاسٍ عَنِ ابْنِ عَبَّاسٍ، قَالَ لَمَّا أَرَادُوا أَنْ يَحْفِرُوا، لِرَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَكَانَ أَبُو عُبَيْدَةَ بْنُ الْجَرَّاحِ يَضْرَحُ كَحَفْرِ أَهْلِ مَكَّةَ وَكَانَ أَبُو طَلْحَةَ زَيْدُ بْنُ سَهْلٍ يَحْفِرُ لِأَهْلِ الْمَدِينَةِ فَكَانَ يَلْحَدُ فَدَعَا الْعَبَّاسُ رَجُلَيْنِ فَقَالَ لِأَحَدِهِمَا اذْهَبْ إِلَى أَبِي عُبَيْدَةَ وَلِلْآخَرِ اذْهَبْ إِلَى أَبِي طَلْحَةَ اللَّهُمَّ خِرْ لِرَسُولِكَ قَالَ فَوَجَدَ صَاحِبُ أَبِي طَلْحَةَ أَبَا طَلْحَةَ فَجَاءَ بِهِ فَلَحَدَ لِرَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ‏.‏