He was sitting with the Prophet ﷺ when he said, "No one's prayer is complete until he performs ablution thoroughly as Allah the Exalted has commanded him, washing his face and his hands up to the elbows, and wiping his head, and washing his feet up to the ankles."
حدثنا محمد بن يحيى حدثنا حجاج حدثنا همام حدثنا إسحق بن عبد الله بن أبي طلحة حدثني علي بن يحيى بن خلاد عن أبيه
أنه كان جالسا عند النبي ﷺ فقال إنها لا تتم صلاة لأحد حتى يسبغ الوضوء كما أمره الله تعالى يغسل وجهه ويديه إلى المرفقين ويمسح برأسه ورجليه إلى الكعبين
[Its isnad is sahih] Abu Dawud narrated it in the Book of Prayer, chapter on the prayer of one who does not straighten his back in ruku and sujud, hadith no. 858, from the hadith of Hajjaj through this route, and Hakim graded it sahih, as did Dhahabi.