When Paul calls the power of Christ which changed him from great sinner to great apostle — when he calls this power "mercy," he exalts not himself but the Savior. The Christmas gift of change is always a gift, and never a wage. It can never be boasted in. It can be sought after the way a helpless, hungry man seeks food; and it can be accepted by faith. But it can never be earned. And so none of the changes God gives can be the basis of pride. The more like Christ you become, the more you exalt Christ and not yourself.
What God did on the first Christmas and what he does in forgiving and changing people today he did and does in utterly free, sovereign mercy, so that all his people will end the paragraphs of their lives with the words like 1 Timothy 1:17: "To the King of ages, immortal, invisible, the only God, be honor and glory for ever and ever. Amen."
We are not saved from sin and changed into righteousness for the sake of pride but for the sake of praise. And when God's work on us is done and we stand perfected before Christ in the last day, we will not exult in our worth but will sing with millions of angels: "Worthy is the Lamb that was slain, to receive power and wealth and wisdom and honor and glory and blessing." Praise to you, O Lord. Amen.
Excerpted from Christ Jesus Came into the World to Save Sinners (1983).