Al-Qasim (may Allah have mercy on him) says that Sayyidah Aishah (may Allah be pleased with her) said: This is the tashahhud of the Prophet (peace and blessings be upon him): 'At-tahiyyatu lillahi was-salawatu wat-tayyibat, as-salamu 'alayka ayyuhan-nabiyyu wa rahmatullahi wa barakatuh, as-salamu 'alayna wa 'ala 'ibadillahis-salihin, ashhadu an la ilaha illallah, wa ashhadu anna Muhammadan 'abduhu wa rasuluh' (All verbal, physical and financial acts of worship, every one of them, are due to Allah. O Prophet (peace and blessings be upon him), peace be upon you, and the mercy of Allah and His blessings. Peace be upon us and upon all the righteous servants of Allah. I bear witness that there is no god but Allah, and I bear witness that Muhammad (peace and blessings be upon him) is the servant of Allah and His Messenger). Muhammad (may Allah have mercy on him) says: I said: 'Bismillah'? Al-Qasim (may Allah have mercy on him) said: 'Bismillah' is (said) at all times.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2843