The Messenger of Allah ﷺ taught us how to pray. He stood and pronounced the takbir, and when he intended to bow, he placed his hands together between his knees and bowed.When this reached Saad, he said, "My brother has spoken the truth. We used to do this, then we were commanded to do this," meaning grasping the knees.
أخبرنا نوح بن حبيب قال أنبأنا ابن إدريس عن عاصم بن كليب عن عبد الرحمن بن الأسود عن علقمة
علمنا رسول الله ﷺ الصلاة فقام فكبر فلما أراد أن يركع طبق يديه بين ركبتيه وركع فبلغ ذلك سعدا فقال صدق أخي قد كنا نفعل هذا ثم أمرنا بهذا يعني الإمساك بالركب
[Its chain is sahih] Abu Dawud narrated it in the Book of Prayer, chapter titled "One Who Mentioned That He Raises His Hands When He Stands Up from Two Prostrations," hadith 747, from the hadith of Abdullah bin Idris with this wording, and it is found in Kubra, hadith 620. Muslim and others also narrated it from the hadith of Alqama and others, from Abdullah bin Masud, with similar wording.