Musnad Ahmad Hadith 23258

Zaid bin Wahb narrates that once Hudhaifa (may Allah be pleased with him) entered the mosque and saw that near the doors of Kindah, a man was praying. He was not performing the bowing (ruku) and prostration (sajdah) properly. When he finished the prayer, Hudhaifa (may Allah be pleased with him) asked him, "Since when have you been praying like this?" He replied, "For forty years." Hudhaifa (may Allah be pleased with him) said, "You have not prayed a single prayer in forty years, and if you were to depart from this world with this prayer, you would not die upon the nature (fitrah) which was granted to the Noble Prophet (ﷺ)." Then he began to teach him the prayer and said, "A person should pray lightly, but should complete the bowing and prostration."