Sahih Muslim , Book 35, Hadith 6555 (USC-MSA) ⓘ
This hadith has been narrated on the authority of Ubaidullah b. Umar with the same chain of transmitters and he said: Then utter:" My Lord. with Thine name I place my side and if Thou keepest me alive have mercy upon myself"
وَحَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا عَبْدَةُ، عَنْ عُبَيْدِ اللَّهِ بْنِ عُمَرَ، بِهَذَا الإِسْنَادِ وَقَالَ " ثُمَّ لْيَقُلْ بِاسْمِكَ رَبِّي وَضَعْتُ جَنْبِي فَإِنْ أَحْيَيْتَ نَفْسِي فَارْحَمْهَا " .
also referenced under: Book 48, Hadith 86 (In-Book) & Hadith 2714 (Reference)