Muwatta Malik, Book 9, Hadith 71 (USC-MSA) ⓘ
Yahya related to me from Malik that Abdullah ibn Dinar said, "I saw Abdullah ibn Umar stop by the grave of the Prophet, may Allah bless him and grant him peace, and ask for blessings on the Prophet, may Allah bless him and grant him peace, and on Abu Bakr and Umar."
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، قَالَ رَأَيْتُ عَبْدَ اللَّهِ بْنَ عُمَرَ يَقِفُ عَلَى قَبْرِ النَّبِيِّ صلى الله عليه وسلم فَيُصَلِّي عَلَى النَّبِيِّ صلى الله عليه وسلم وَعَلَى أَبِي بَكْرٍ وَعُمَرَ .
also referenced under: Book 9, Hadith 402 (In-Book)