During the first century A.D., Mithraism is the dominant faith in the places Paul travels to. Is it not probable that early Christianity was mirrored after this pagan faith in order to gain new converts?
Mithraism was indeed a rather popular religion in the first century A.D., but there is no evidence that it influenced early Christian practice or doctrine at all. Early Christianity was a development out of early Judaism. It is indebted to the various forms of early Judaism, not to pagan religions.
—Ben Witherington III