Muwatta Malik 168

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي نُعَيْمٍ، وَهْبِ بْنِ كَيْسَانَ عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، أَنَّهُ كَانَ يُعَلِّمُهُمُ التَّكْبِيرَ فِي الصَّلاَةِ ‏.‏ قَالَ فَكَانَ يَأْمُرُنَا أَنْ نُكَبِّرَ كُلَّمَا خَفَضْنَا وَرَفَعْنَا ‏.‏

Yahya related to me from Malik from Abu Nuaym Wahb ibn Kaysan that Jabir ibn Abdullah used to teach them the takbir in the prayer. Abu Nuaym said, "He used to tell us to say 'Allah is greater' whenever we lowered or raised ourselves

Reference

Muwatta Malik 168

In-book

Book 3, Hadith 1