You have heard of my career and former manner of life in Judaism, how I used to hunt down and persecute the church of God extensively and [with fanatical zeal] tried [my best] to destroy it.

they merely heard that 'our former persecutor is now preaching the faith he once harried,'

But at that former time, as you did not know the true God, you were slaves to gods that do not really exist,

but you knew I preached the gospel to you on my former [visit] in weakness of the flesh,

My little children, of whom I travail in birth again until Christ be formed in you,

till Christ be formed in you, I should be glad to be present with you even now, and to change my voice; for I am in doubt about you.