John Calvin regarded the Anabaptist notion of re-baptism as a great evil:

[W]e are baptised only once, and if we return for a second baptism, this is in effect wishing to negate the true baptism which was ordained by God […]

John Calvin, Sermons on 2 Samuel: chapters 1-13, trans. D. F. Kelly (Edinburgh, 1992), p. 56.