Biblical commentators have identified the three men who appeared to Abraham in Genesis as either three angels or two angels accompanied by Jesus. In the verse, Genesis 18:2, Abraham rushes to greet the three visitors and bows before them.
Ellicott's Commentary for English Readers explains that, according to Jewish belief, an angel could not take on more than one duty at a time. Three angels therefore appeared to Abraham because one was sent to heal him, one to give a message to his wife Sarah, and one to bring destruction to Sodom.
On the other hand, the Benson Commentary and Gill's Exposition of the Entire Bible speculate that one of the visitors was Jesus Christ. Gill's Exposition also mentions a Talmudic interpretation according to which the three angels are Michael, Gabriel and Raphael.