NOTES for Act 2:36-41
Peter's answer to the question of what Christianity is and what a Christian should do sounds completely clear. First of all, it is a matter of repentance for sins committed and of washing in the name of Jesus Christ, which frees a person from these sins and from their consequences once and for all. And then a new life begins, life in the Kingdom, inseparable from what the apostle calls "the gift of the Holy Spirit." That is how the Synodal Translation reads. But the Greek text allows another, more convincing interpretation: receive a gift from God, the Holy Spirit.
The divine breath that permeates the Kingdom is the chief gift to Christians from God. A gift received through Christ, in union with Him as King of this Kingdom. Here lies the answer to the question of what a Christian should do. Live. Live in the Kingdom. If Christianity were some new religion, the question of what its adherents should do would be entirely appropriate. But the point is that Peter is not speaking about religion. In the religious sense he offers his hearers nothing new. Even the washing, or as it is commonly called in English, baptism, of Christians is only one form of the cleansing washings that existed in those days.
The difference here is not in the religious form, but in the content, in what was connected with the washing. Here there was not simple cleansing, but a cleansing in which those being cleansed asked the Savior Himself for cleansing. So that afterward those cleansed would be bound to Him and could share in the life of that Kingdom of which He is King. The cleansing washing here became a kind of pass into the Kingdom.
But this was only the first step, and afterward one had to live in the Kingdom. To live so that the Christian's heart becomes the place where the Kingdom abides. So that it would be not only around, but also within. Because otherwise it does not happen; otherwise one cannot share in the life of the Kingdom. The breath of the Kingdom entering the Christian's heart becomes the chief gift from God. Now one must learn to live with this gift, to live so as not to lose it. This is the chief Christian discipline: the science of life in the Kingdom, the science of acquiring and preserving in one's heart God's gift, the breath of the Kingdom.