John Calvin Commentary 1 John 2:24

"As for you, let that abide in you which ye heard from the beginning. If that which ye heard from the beginning abide in you, ye also shall abide in the Son, and in the Father." — 1 John 2:24 (ASV)

Let that therefore abide in you. He adds an exhortation to the previous doctrine; and to give it more weight, he points out the fruit they would receive from obedience. He then exhorts them to persevere in the faith, so that they might retain fixed in their hearts what they had learned.

But when he says, from the beginning, he does not mean that antiquity alone was sufficient to prove any doctrine true. Instead, as he has already shown that they had been rightly instructed in the pure gospel of Christ, he concludes that they should rightly continue in it. And this order should be especially noted; for if we were unwilling to depart from that doctrine which we have once embraced, whatever it might be, this would not be perseverance, but perverse obstinacy. Therefore, discernment should be exercised, so that a reason for our faith may be made evident from God’s word; then inflexible perseverance should follow.

The Papists boast of a beginning because they have absorbed their superstitions from childhood. Under this pretense, they allow themselves obstinately to reject the plain truth. Such perverseness shows us that we should always begin with the certainty of truth.

In that which you have heard. Here is the fruit of perseverance: that they in whom God’s truth remains, remain in God. From this we learn what we are to seek in every truth pertaining to religion. Therefore, he makes the greatest proficiency who makes such progress as to cleave wholly to God. But he in whom the Father does not dwell through his Son is altogether vain and empty, whatever knowledge he might possess. Moreover, this is the highest praise of sound doctrine: that it unites us to God, and that in it is found whatever pertains to the real fruition of God.

Finally, he reminds us that it is real happiness when God dwells in us. The words he uses are ambiguous. They may be rendered, This is the promise which he has promised to us, even eternal life. You may, however, adopt either of these renderings, for the meaning is still the same. The sum of what is said is that we cannot live otherwise than by nourishing to the end the seed of life sown in our hearts. John greatly insists on this point: that not only the beginning of a blessed life is to be found in the knowledge of Christ, but also its perfection. But no repetition of it can be too much, since it is well known that it has always been a cause of ruin for people when, not content with Christ, they have had a craving to wander beyond the simple doctrine of the gospel.