The Prophet ﷺ said, "Complete the bowing and prostration thoroughly when you bow and prostrate."
أخبرنا محمد بن عبد الأعلى قال حدثنا خالد قال حدثنا شعبة عن قتادة قال سمعت
عن النبي ﷺ قال أتموا الركوع والسجود إذا ركعتم وسجدتم
Sourcing, its isnad is sahih. It is in Kubra, no. 641. Bukhari also narrated it in the chapter on adhan, in the chapter on humility in prayer, no. 742, no. 6644, and Muslim in the chapter on prayer, in the chapter on the command to perfect prayer, complete it, and observe humility in it, no. 110/425, from the hadith of Shuba, with it in full.