ʿAbdullāh ibn ʿUmar said: “The Messenger of Allah ﷺ went out to Qubā to pray there. The Ansār came to him and greeted him while he was praying. I asked Bilāl, ‘How did you see the Messenger of Allah ﷺ respond to them when they greeted him while he was praying?’ He replied, ‘Like this.’” Jaʿfar ibn ʿAwn extended his hand, with his palm facing downward and the back of his hand upward. This is recorded in the Sunan collections and the Musnad (1). Al-Tirmidhī graded it authentic; his wording is: “He would gesture with his hand.”
ʿAbdullāh ibn Masʿūd said: “When I returned from Abyssinia, I came to the Prophet ﷺ while he was praying. I greeted him, and he gestured with his head.” Al-Bayhaqī cited this (2).
As for the hadith transmitted by Abū Ghatfān from Abū Hurayrah, who reported that the Messenger of Allah ﷺ said, “Whoever makes a gesture during his prayer that conveys an intelligible meaning must repeat his prayer,” it is a baseless hadith, cited by al-Dāraqutnī (3)
(1) This is what he stated, but I found it only in the Sunan collections, as noted in the preceding source references; the wording is Abū Dāwūd’s. In the report narrated by Ahmad (4586), the questioner is Ibn ‘Umar, as already noted in those references.
(2) In al-Sunan al-Kubrā (2:368), through Muhammad ibn Sīrīn from Ibn Mas‘ūd. Al-Bayhaqī said: “This is the correctly preserved version; its chain is disconnected (mursal).” He then cited a version through Abū Ya‘lā al-Tawzī—also reported by al-Sarrāj in his Hadīth (948)—with Abū Hurayra inserted between Ibn Sīrīn and Ibn Mas‘ūd, and said: “Abū Ya‘lā alone transmitted this version.” Ibn al-Madīnī likewise rejected presenting its chain as connected by inserting Abū Hurayra, saying: “It is only from Ibn Sīrīn, who related that Ibn Mas‘ūd…” This is cited in Ibn Rajab’s Fath al-Bārī (6:322). The disconnected version is strengthened by the account of Ibn Mas‘ūd’s return from Abyssinia and his greeting to the Prophet (peace and blessings be upon him), reported by Ibn Abī Shayba (4854) and Abū Dāwūd in his Marāsīl (p. 98), through two disconnected chains from Ibn Sīrīn.
(3) Nos. 1866 and 1867; al-Bayhaqī also reported it through him (2:262). Al-Dāraqutnī’s comments follow no. 1867 and also mention that Ibn Abī Dāwūd considered it likely that the wording in question was Ibn Ishāq’s own statement. Abū Hātim likewise graded it weak in al-‘Ilal (199), attributing its defect to Ibn Ishāq. It was also reported by Ishāq ibn Rāhawayh (543), Abū Dāwūd (944), and al-Bazzār (15:116). Abū Dāwūd said: “This hadith is an error.”