Musnad Ahmad 1153:864

Ahmad ibn Abd al-Malik narrated to us, he said: Salam ibn Abi Muti’ narrated to us, from Jabir ibn Yazid al-Ju’fi, from ‘Amir, from Yahya ibn al-Jazzar, from ‘Aishah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever washes a deceased person, and fulfills the trust regarding him, and does not disclose what he sees of him during that, he will emerge from his sins like the day his mother gave birth to him." He said: "His family is the closest of you to him if he has knowledge [of how to wash]. If he does not have knowledge, then [it should be] whoever you see among you who possesses a share of piety and trustworthiness."