It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) hesitated while reciting a verse in the Fajr prayer. When he (peace and blessings be upon him) finished the prayer, he looked at the faces of those present and asked: "Did Ubayy bin Ka'b not pray with you?" The people said: No. The people then understood that he (peace and blessings be upon him) had asked about him only so that he could correct him (peace and blessings be upon him) (by prompting him in the recitation).
Imam al-Harith recorded this report in his Musnad (Bughyat al-Bahith: 424). Its chain contains Qays bin al-Rabi', who has been graded da'if (weak) because of his poor memory; however, the mention of Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) in connection with prompting in prayer is also found in other reliable hadith that support its meaning.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الصلاة / 424
Hadith Gradingمحدثین:إسناده حسن
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :إسناده حسن لغيره. » «أخرجه المعجم الكبير للطبراني برقم: 12665، وأخرجه المعجم الأوسط للطبراني برقم: 5927، وأخرجه مجمع الزوائد ومنبع الفوائد برقم: 2356، وأخرجه إتحاف الخيرة المهرة بزوائد المسانيد العشرة برقم: 1062»