Mishkat al-Masabih 947
Al-Bara’ said:
When we prayed behind God’s Messenger we liked to be on his right side so that he would turn his face towards us. He said that he had heard him say, ‘My Lord, guard me from Thy punishment on the day Thou raisest (or, gatherest) Thy servants.” 

Muslim transmitted it.
وَعَنِ الْبَرَاءِ قَالَ: كُنَّا إِذَا صَلَّيْنَا خَلْفَ سَوَّلَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَحْبَبْنَا أَنْ نَكُونَ عَنْ يَمِينِهِ يُقْبِلُ عَلَيْنَا بِوَجْهِهِ قَالَ: فَسَمِعْتُهُ يَقُولُ: «رَبِّ قِنِي عَذَابَكَ يَوْمَ تَبْعَثُ أَو تجمع عِبَادك» . رَوَاهُ مُسلم