Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) hesitated over a verse in the Fajr prayer. When he completed the prayer, he looked at the people and asked: "Did Ubayy bin Ka'b not pray with you?" The people said: "No." The narrator says: The people understood that the Prophet (peace and blessings be upon him) had asked about him because he would have prompted him.
Al-Bazzar recorded it, and al-Tabarani recorded it in al-Mu'jam al-Kabir and al-Mu'jam al-Awsat. Its narrators are all thiqat (trustworthy) except Qays bin al-Rabi', whom Yahya al-Qattan and others declared da'if (weak), while Shu'bah and al-Thawri declared him thiqah (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2356