John the Apostle
1 John 2:24ESV·traditional attribution

Let what you heard from the beginning abide in you. If what you heard from the beginning abides in you, then you too will abide in the Son and in the Father.

John Calvin Reformed @genevareformer

24 Let that therefore abide in you He annexes an exhortation to the former doctrine; and that it might have more weight, he points out the fruit they would receive from obedience. He then exhorts them to perseverance in the faith, so that they might retain fixed in their hearts what they had learnt.

Matthew Henry Presbyterian @wholebiblehenry

Here, I. The apostle encourages the disciples (to whom he writes) in these dangerous times, in this hour of seducers; he encourages them in the assurance of their stability in this day of apostasy: But you have an unction from the Holy One, and you know all things. We see, 1. The blessing wherewith they were enriched - an unguent from heaven: You have an unction.

Commenting on 1 John 2:20-27

John Gill Reformed Baptist @doctorgill

Let that therefore abide in you,.... Meaning the word of God, 1Jo_2:14; the Gospel of Christ, which there was reason to believe had a place in their hearts, and which they had embraced and professed; and therefore the apostle exhorts them to perseverance in it; and particularly not to let go the doctrine concerning the Father and the Son, and this their relation to each...