An-Nu‘man b. Murra reported Allah's Messenger ﷺ as saying, “What do you think of the drinker, the fornicator, and the thief?” That was before the prescribed punishments regarding them were revealed. On receiving the reply that Allah and His Messenger knew best, he said, “Such sins are abominations and punishment is prescribed for them, but the worst theft is what one steals from his prayer.” He was asked how one could steal from his prayer and replied, “By not performing his bowing and his prostration perfectly.” Malik and Ahmad transmitted it, and Darimi transmitted something similar.