When Peter stands up in the midst of the 120 and declares that Judas must be replaced, he was speaking the truth (Acts 1:20). It is true from Scripture that God intended to someday replace Judas. But that doesn't mean it was the right time to decide who the Lord had chosen to become part of the Twelve. What happened then, and what often happens with each of us, is that we decide a course of action, present God with two options we have chosen, and then ask Him to choose which of our choices is His will. And this assumes it was His will for us to do what we've determined to do in the first place.
The lesson from Acts 1:15-26 is that doing the right thing, at the wrong time, is the wrong thing. Everytime. No matter how much it feels like the right thing and the right time.
And it often takes years to undo the mistakes we make for the right reason, or so we think. Remember, spiritual maturity is asking God what His will is, and not trying to force Him to choose the lesser of two evils that we have chosen. Do you want to know more about this classic error of presumption? Then keep listening.
The following is a study on Acts 1:15-26.