Muwatta Malik, Book 45, Hadith 25 (USC-MSA)

Yahya related to me from Malik from Ibn Shihab from Salim ibn Abdullah that Umar ibn al-Khattab turned people back at Sargh according to the hadith of Abd ar-Rahman ibn Awf.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، إِنَّمَا رَجَعَ بِالنَّاسِ مِنْ سَرْغَ عَنْ حَدِيثِ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ، ‏.‏

sunnah.com

also referenced under: Book 45, Hadith 1624 (In-Book)