“And if any man sin, we have an Advocate with the Father, Jesus Christ the righteous.” This is to prevent despair.
It is here supposed, that though it is the habitual aim of true Christians not to sin, yet, in this world, they are not free from it. Some have fallen into grievous sins, as we too well know, from Scripture, observation, and, in many instances, from painful experience. Others, who have not fallen so as either to disgrace themselves or the name of Christ, yet have much sin wherewith to reproach themselves, in deeds, or words, or unlawful desires. The petition in the Lord’s prayer, “Forgive us our trespasses,” shows that we sin, and need forgiveness, as often as we need our daily bread. If any man imagine himself to have arrived to sinless perfection, he must be wofully blind to the spirituality of the Divine law, and to the extent of his obligations. “If we say that we have no sin, we deceive ourselves, and the truth is not in us.”
Further, It is here suggested that, whatever be our sin, yet if we confess it with a contrite heart, and believe in Jesus who died for sinners, and rose from the dead, and ascended to the Father, he will be our Advocate, and our sins shall be forgiven for his sake. It was in this way that David was forgiven. It is true, Christ had not then died, nor risen, nor ascended to be the Advocate with the Father; but his penitential prayer shows that he believed in him according to the light that he possessed, which might be much greater than we imagine. His prayer to be purged with hyssop, doubtless, alluded to the purgations under the law, by dipping a bunch of hyssop in blood, and sprinkling it upon the unclean; but as none of these ceremonial cleansings were admissible in cases of adultery or murder, he cannot be understood as speaking literally. He must, therefore, have believed in a purgation of which this was only a shadow.
It was in this way that the Israelites were forgiven, when praying with their hands spread towards the temple. It was not to the building that they directed their prayer, but to him who dwelt therein, between the cherubim, upon the mercy-seat. It was to the Lord God of Israel, as thus dwelling upon the mercy-seat, that Jonah, at the last extremity, looked and lived: “Then I said, I am cast out of thy sight; yet I will look again toward thy holy temple.”
In this way, whatever sins we have committed, we must seek for mercy; and for our encouragement, we are assured of an “Advocate with the Father, Jesus Christ the righteous.”
Fuller, A. G. (1988). Excerpt from: “Christianity and the Antidote to Presumptions and Despair,” Sermon XXIV. The Complete Works of Andrew Fuller: Memoirs, Sermons, Etc. (J. Belcher, Ed.; Vol. 1, pp. 324–325). Sprinkle Publications.