19 By this we shall know that we are of the truth and reassure our heart before him; 20 for whenever our heart condemns us, God is greater than our heart, and he knows everything. 21 Beloved, if our heart does not condemn us, we have confidence before God; 22 and whatever we ask we receive from him, because we keep his commandments and do what pleases him.
This is a passage talking about assurance. Now we who have been involved in the C/A debate know about assurance. Calvinists often say that they are assured of their salvation because they have been predestined before the foundation of the world, and know that they cannot loose what they have been given.
But this is not the kind of assurance that John is talking about here; John is not concerned about whether you know you will keep what you have obtained, but he is concerned about us knowing that we have obtained it to begin with. It is not whether or not we will remain in the truth, but whether or not we are already “of the truth”. Arminians agree that this is true assurance.
The “by this” recalls the rhetoric used in verse 16, but unlike in 16, it is calling us backward, not forward to determine what “this” is. John is still referring to love, and who love demonstrates itself by deed. Though our deeds do not merit us in salvation, they do mark us as Christians. The future tense here is referring to any possible situation in this life where our conscience causes us to doubt our salvation. However, we should not doubt.
We should not pray the sinner’s prayer every single time that we are convicted of something we did, or because rebaptized because we just “feel that we should”. I’ve seen too much of this in my life.
God is supposed to be bigger than our doubts. When we doubt, then we are supposed to trust in the work of God which has come before. We are to trust in Him, and pray to Him. If we are living by love, and if we are walking in His ways, we are assured that God will hear our prayers and honor our repentance. There is never a reason to doubt, for our God is a gracious God abounding in mercy and love. We keep the faith a press on.