Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said that I saw the Messenger of Allah (peace and blessings be upon him) saying «الله اكبر» every time he rose, bent down, stood, and sat.
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1283
Hadith Takhrijاس حدیث کی سند صحیح ہے۔ دیکھئے: [نسائي 1145] ، [مسند أبى يعلی 5101، 5128]
Brief Explanation
(Commentary on Hadiths 1281 to 1283) From these hadiths, it is established that when moving from one pillar (rukn) of the prayer to another, one should say "Allahu Akbar" (Allah is the Greatest), except when rising from bowing (ruku‘), when one should say «سَمِعَاللّٰهُلِمَنْحَمِدَه» (i.e., Allah has heard the one who praised Him). The jurists (fuqaha) and scholars have included all the takbirs after the opening takbir (takbir al-tahrimah), saying «سَمِعَاللّٰهُلِمَنْحَمِدَهُرَبَّنَاوَلَكَالْحَمْدُ», the tasbihat (glorifications) of bowing (ruku‘) and prostration (sujud), all among the obligatory acts (wajibat) of the prayer. If an individual praying alone (munfarid) or the imam forgets to say these, then he must perform the prostration of forgetfulness (sujud al-sahw). And Allah knows best.