Yahya related to me from Malik from Nafi that he heard Abdullahibn Umar making dua on Safa saying, "O Allah, You have said, 'call onMe - I will answer you' and You do not break Your promise. So I amaskingYou, in the same way that You have guided me to Islam, not totake it away from me, and that You make me die while I am muslim."
USC-MSA web (English) reference: Book 20, Hadith 129
Arabic reference: Book 20, Hadith 832