Sayyidah Aishah (may Allah be pleased with her) says: When the Messenger of Allah (peace and blessings be upon him) fell ill with the illness in which he (peace and blessings be upon him) passed away, the call to prayer was given. She mentioned the whole story, but did not mention her words to Sayyidah Hafsah (may Allah be pleased with her). She says: The Messenger of Allah (peace and blessings be upon him) came out, then he (peace and blessings be upon him) was praying sitting, and Sayyiduna Abu Bakr (may Allah be pleased with him) was beside him (peace and blessings be upon him); Sayyiduna Abu Bakr (may Allah be pleased with him) was conveying his (peace and blessings be upon him) takbirs to the people.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5080