(a) Sayyiduna Abdullah bin Abd al-Rahman bin Abza narrates from his father (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) did not say the takbir in full.
(b) In the narration of Amr, Sayyiduna Ibn Abd al-Rahman bin Abza narrates from his father that he prayed with the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) did not say the takbir in full.
(c) Here it is also possible that he (peace and blessings be upon him) said the takbir and he did not hear it, or it may be that he (peace and blessings be upon him) left it out once or twice to show that this is permissible.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2500