Matthew Henry Commentary Acts 2:37-41

"Now when they heard [this,] they were pricked in their heart, and said unto Peter and the rest of the apostles, Brethren, what shall we do? And Peter [said] unto them, Repent ye, and be baptized every one of you in the name of Jesus Christ unto the remission of your sins; and ye shall receive the gift of the Holy Spirit. For to you is the promise, and to your children, and to all that are afar off, [even] as many as the Lord our God shall call unto him. And with many other words he testified, and exhorted them, saying, Save yourselves from this crooked generation. They then that received his word were baptized: and there were added [unto them] in that day about three thousand souls." — Acts 2:37-41 (ASV)

From the first delivery of that Divine message, it appeared that Divine power accompanied it, and thousands were brought to the obedience of faith. But neither Peter's words nor the miracle they witnessed could have produced such effects if the Holy Spirit had not been given. Sinners, when their eyes are opened, cannot help but be pricked to the heart for sin and cannot help but feel an inward uneasiness.

The apostle exhorted them to repent of their sins and openly avow their belief in Jesus as the Messiah by being baptized in his name. Thus, by professing their faith in Him, they would receive remission of their sins and partake of the gifts and graces of the Holy Spirit. Separating from wicked people is the only way to save ourselves from them. Those who repent of their sins and give themselves up to Jesus Christ must prove their sincerity by breaking off from the wicked.

We must save ourselves from them; this means avoiding them with dread and holy fear. By God's grace, three thousand persons accepted the gospel invitation. There can be no doubt that the gift of the Holy Spirit, which they all received and from which no true believer has ever been shut out, was that Spirit of adoption, that converting, guiding, sanctifying grace, which is bestowed upon all the members of the family of our heavenly Father. Repentance and remission of sins are still preached to the chief of sinners in the Redeemer's name; still the Holy Spirit seals the blessing on the believer's heart; still the encouraging promises are to us and our children; and still the blessings are offered to all who are far off.