Acts 15:8-9 says “So God, who knows the heart, acknowledged them by giving them the Holy Spirit, just as He did to us, and made no distinction between us and them, purifying their hearts by faith.”
Their hearts were purified by their believing right—believing that those who believed in the Lord would receive the remission of sins and be made the righteousness of God.
How are we made righteous today? How are our hearts purified today? By faith in our Lord’s finished work at the cross!
In the Sermon on the Mount, Jesus said, “Blessed are the pure in heart, for they shall see God” (Matt. 5:8). Now you are equipped to answer this question: who are the pure in heart? Those whose hearts have been purified by faith. Amen! This is how we use Scripture to interpret Scripture.