World Wide Study Bible
a Bible passage
19 And hereby we know, or, by this we know. The word truth, he takes now in a different sense; but there is a striking similarity in the words, — If we, in truth, love our neighbors, we have an evidence that we are born of God, who is truth, or that the truth of God dwells in us. But we must ever remember, that we have not from love the knowledge which the Apostle mentions, as though we were to seek from it the certainty of salvation. And doubtless we know not otherwise that we are the children of God, than as he seals his free adoption on our hearts by his own Spirit., and as we receive by faith the sure pledge of it offered in Christ. Then love is accessory or an inferior aid, a prop to our faith, not a foundation on which it rests.
Why then does the Apostle say, We shall assure our hearts before God? He reminds us by these words, that faith does not exist without a good conscience; not that assurance arises from it or depends on it, but that then only we are really and not falsely assured of our union with God, when by the efficacy of his Holy Spirit he manifests himself in our love. For it is ever meet and proper to consider what the Apostle handles; for as he condemns feigned and false profession of faith, he says that a genuine assurance before God we cannot have, except his Spirit produces in us the fruit of love. Nevertheless, though a good conscience cannot be separated from faith, yet no one should hence conclude that we must look to our works in order that our assurance may be certain.