Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) was given his ritual bath (ghusl) in a shirt, and those who went down into his (peace and blessings be upon him) grave were Ali, al-Fadl bin Abbas, Salih bin Abbas and Salih bin Shuqran, the freed slave of the Messenger of Allah (peace and blessings be upon him) (may Allah be pleased with them).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10753