Muwatta Imam Malik Book of Hajj, Hadith 129

Yahya related to me from Malik from Nafi that he heard Abdullah ibn Umar making dua on Safa saying, "O Allah, You have said, 'call on Me - I will answer you' and You do not break Your promise. So I am askingYou, in the same way that You have guided me to Islam, not to take it away from me, and that You make me die while I am muslim."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّهُ سَمِعَ عَبْدَ اللَّهِ بْنَ عُمَرَ، وَهُوَ عَلَى الصَّفَا يَدْعُو يَقُولُ اللَّهُمَّ إِنَّكَ قُلْتَ ادْعُونِي أَسْتَجِبْ لَكُمْ وَإِنَّكَ لاَ تُخْلِفُ الْمِيعَادَ وَإِنِّي أَسْأَلُكَ كَمَا هَدَيْتَنِي لِلإِسْلاَمِ أَنْ لاَ تَنْزِعَهُ مِنِّي حَتَّى تَتَوَفَّانِي وَأَنَا مُسْلِمٌ .