The second reason why God has connected salvation with baptism in the NT
age has to do with our need for a personal assurance that God has indeed saved
us. Sometimes it is easy to be plagued by doubts and uncertainties as to
whether we have truly met the God of our salvation and have truly received his
gifts of saving grace. We know what God has promised, but has it really
happened to us?
As a concession to our human frailty in this respect, God has tied his
promises to baptism as a concrete, objective event that will always stand out
in our memories. It is an unforgettable reference point to which we can always
return when we begin to doubt that we have received God’s grace. It is the
“stake” that God himself has provided for our comfort and assurance. We do not
have to torture ourselves, wondering at what point our faith was strong enough
or our repentance sincere enough to be saved. The sufficiency for our salvation
lies in the power of God and the truth of his promises. He has promised to save
us in baptism. Just as surely we can remember our baptism, so we can be sure
that God has kept his promises to us.
This is the sense in which there is a psychological connection between
baptism and salvation. Knowing that we have been baptized has a definite effect
on our state of mind, in the sense that it undergirds our assurance of
salvation. This psychological effect is possible, though, only because baptism
is in itself the time when salvation is given. (Jack Cottrell, The Faith
Once for All: Bible Doctrine for Today [College Press, 2002, 2023], 370-71)
