Sayyidah Aishah (may Allah be pleased with her) says that when the Prophet (peace and blessings be upon him) grew older and his body became heavier, he (peace and blessings be upon him) used to pray seven rak'ahs, reciting the tashahhud in the sixth rak'ah, praising and glorifying Allah and supplicating to Allah; then he would stand up, but would not say the salam. Then he would sit in the seventh rak'ah, praise Allah and supplicate to Allah, then say a salam loud enough for us to hear. Then he would pray two rak'ahs sitting. O son, that made nine rak'ahs.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4811