Imam Ahmad also records (2/68): “Affan related to us; Aban b. Yazid related to us; Qatadah related to us; he said: Abd Allah b. Babi al-Makki told me: ‘I prayed beside Abd Allah b. Umar. When he finished the prayer he struck his thigh with his hand and said, “Shall I not teach you the greeting (tahiyyah) of the prayer just as the Messenger of Allah used to teach us?” He then recited to me these words’—that is, the formula transmitted by Abu Musa al-Ashari in the tashahhud.” Ahmad gives it in this form, and its isnad is sound according to Muslim’s criteria. Al-Tahawi (1/155) also transmits it through Ibn Marzuq, who said: “Affan b. Muslim related to us …,” but adds: “He then recited these words, like the wording in Ibn Masud’s hadith from the Prophet.” In my judgement Ahmad’s version is more reliable than Ibn Marzuq’s. Thus both of the additional phrases ultimately trace back to the Prophet within Ibn Umar’s narration, though he did not hear them from the Prophet directly; they reached him through Abu Musa. This is the only plausible way to reconcile the two versions of Ibn Umar’s report. Allah knows best.