Here, the word coffin may refer to:
a long box in which someone is buried, or
a funeral bier (a frame or portable stand used to carry the coffin or the body of the person who had died).
A Jew became ceremonially unclean by touching a dead body, coffin, or bier (Leviticus 21:1, 11–12). But when Jesus touched the man with leprosy, he did not become unclean (Luke 5:13). Instead, he replaced disease and death with cleansing and life.