Sunan Ibn Majah Book 5, Hadith 88
“The Messenger of Allah (ﷺ)
said: ‘When anyone of you bows, let him say in his bowing: “Subhana
Rabbiyal-‘Azim (Glory is to my Lord, the Most Great)” three
times; if
he does that his bowing will be complete. And when anyone
of you
prostrates, let him say in his prostration, ‘Subhana
Rabbiyal-A’la
(Glory if to my Lord, the Most High)” three times;
if he does that,
his prostration will be complete, and that is the
minimum.’”
“The Messenger of Allah (ﷺ) often used to say when bowing and prostrating: ‘Subhanak Allahumma wa bi hamdika, Allahummaghfir li (Glory be to You, O Allah, and praise; O Allah forgive me),’ following the command given by the Qur’an.”[Surat An-Nasr (110)]
The Messenger of Allah (ﷺ) said: “When anyone of you prostrates let him be balanced in prostration, and not spread his arms as a dog does.”