Sayyiduna Mughira bin Shu’bah (may Allah be pleased with him) narrates that the Prophet Muhammad (peace and blessings be upon him) used to stand (i.e., perform many voluntary prayers) so much that his feet would become swollen. It was said to him: O Messenger of Allah! Has Allah not forgiven your past and future sins? The Prophet Muhammad (peace and blessings be upon him) said:“Should I not be a grateful servant?”