Sayyiduna Uqbah bin Amir (may Allah be pleased with him) said: I came with twelve riders until we stayed with the Messenger of Allah (peace and blessings be upon him). My companions said: You graze our camels and we will go and acquire knowledge from the Messenger of Allah (peace and blessings be upon him); then when we return in the evening, we will tell you whatever we have heard from the Messenger of Allah (peace and blessings be upon him). I did so for some days, then I thought to myself: Perhaps I am at a loss; my companions hear what I do not hear and learn from the Prophet of Allah (peace and blessings be upon him) what I do not learn. So one day I attended, and the Prophet of Allah (peace and blessings be upon him) said: "Whoever performs a complete ablution (wudu), then stands for his prayer, becomes as free of his sins as he was on the day his mother gave birth to him."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15000