Musannaf Ibn Abi Shayba 24:148

Abu Usama narrated to us, he said: Isma'il narrated to us, from Qays, who said: There was a rift between Ibn Mas'ud and al-Walid ibn 'Uqbah. Sa'd prayed against them, saying: "O Allah, reconcile between them." So one of them would say to his companion: "Sa'd has been answered regarding us."