John Calvin on 1 John 1:2

2 For (or, and) the life was manifested The copulative is explanatory, as though he had said, “We testify of the vivifying Word, as life has been manifested.” The sense may at the same time be twofold, that Christ, who is life and the fountain of life, has been manifested, or, that life has been openly offered to us in Christ. The latter, indeed, necessarily follows from the former. Yet as to the meaning, the two things differ, as cause and effect. When he repeats, We shew, or announce eternal life, he speaks, I have no doubt, of the effect, even that he announces that life is obtained for us in Christ.

We hence learn, that when Christ is preached to us, the kingdom of heaven is opened to us, so that being raised from death we may live the life of God.

Which was with the Father. This is true, not only from the time when the world was formed, but also from eternity, for he was always God, the fountain of life; and the power and the faculty of vivifying was possessed by his eternal wisdom: but he did not actually exercise it before the creation of the world, and from the time when God began to exhibit the Word, that power which before was hid, diffused itself over all created things. Some manifestation had already been made; the Apostle had another thing in view, that is, that life was then at length manifested in Christ, when he in our flesh completed the work of redemption. For though the fathers were even under the law associates and partakers of the same life, yet we know that they were shut up under the hope that was to be revealed. It was necessary for them to seek life from the death and resurrection of Christ; but the event was not only far remote from their eyes, but also hid from their minds. They depended, then, on the hope of revelation, which at length in due time followed. They could not, indeed, have obtained life, except it was in some way manifested to them; but the difference between us and them is, that we hold him already revealed as it were in our hands, whom they sought obscurely promised to them in types.

But the object of the Apostle is, to remove the idea of novelty, which might have lessened the dignity of the Gospel; he therefore says, that life had not now at length began to be, though it had but lately appeared, for it was always with the Father.

1 John 1:3-7

3. That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship is with the Father, and with his Son Jesus Christ.

3. Quod vidimus et audivimus, annuntiamus vobis, ut et vos societatem habeatis nobiscum, et societas nostra sit cum Patre et cure filio ejus Jesu Christo.

4. And these things write we unto you, that your joy may be full.

4. Et hæc scribimus vobis, ut gaudium vestrum sit completum.

5. This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all.

5. Et haec est promissio quam annuntiamus, quod Deus lux est, et tenebrae in eo non sunt ullae.

6. If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth:

6. Si dixerimus quod societatem habemus cum eo, et in tenebris ambulamus, mentimur, et veritatem non facimus.

7. But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin.

7. Si autem in luce ambulamus, sicut ipse in luce est, societatem habemus inter nos mutuam, et sanguis Jesu Christi filii ejus emundat nos ab omni peccato.