Christ is the Lamb of God
John 1:29

Behold the Lamb of God. The principal office of Christ is briefly but clearly stated; that he takes away the sins of the world by the sacrifice of his death, and reconciles men to God. There are other favors, indeed, which Christ bestows upon us, but this is the chief favor, and the rest depend on it; that, by appeasing the wrath of God, he makes us to be reckoned holy and righteous. For from this source flow all the streams of blessings, that, by not imputing our sins, he receives us into His favor.

By the word Lamb he alludes to the ancient sacrifices of the Law. This had to do with Jews who, having been accustomed to sacrifices, could not be instructed about atonement for sins in any other way than by holding out to them a sacrifice. As there were various kinds of them, he makes one, by a figure of speech, to stand for the whole; and it is probable that John alluded to the paschal lamb. John employed this mode of expression, which was better adapted to instruct the Jews, and possessed greater force; as in our own day, in consequence of baptism being generally practiced, we understand better what is meant by obtaining forgiveness of sins through the blood of Christ, when we are told that we are washed and cleansed by it from our sins. At the same time, as the Jews commonly held superstitious notions about sacrifices, he corrects this fault in passing, by reminding them of the object to which all the sacrifices were directed. It was a very wicked abuse of the institution of sacrifice, that they had their confidence fixed on the outward signs; and John, holding out Christ, testifies that he is the Lamb of God; by which he means that all the sacrifices, which the Jews were accustomed to offer under the Law, had no power whatever to atone for sins, but that they were only figures, the truth of which was manifested in Christ himself.

Who takes away the sin of the world. He uses the word sin in the singular number, for any kind of iniquity; as if he had said, that every kind of unrighteousness which alienates men from God is taken away by Christ. And when he says, the sin Of The World, he extends this favor indiscriminately to the whole human race; that the Jews might not think that he had been sent to them alone. But hence we infer that the whole world is involved in the same condemnation; and that as all men without exception are guilty of unrighteousness before God, they need to be reconciled to him. John the Baptist, therefore, by speaking generally of the sin of the world, intended to impress upon us the conviction of our own misery, and to exhort us to seek the remedy. Now our duty is, to embrace the benefit which is offered to all, that each of us may be convinced that there is nothing to hinder him from obtaining reconciliation in Christ, provided that he comes to him by the guidance of faith.

Although God had appointed the one sacrifice which directed men to Christ; but yet every man contrived for himself his own method of appeasing God. John leads us back to Christ alone, and informs us that there is no other way in which God is reconciled to us than through his agency, because he alone takes away sin. He therefore leaves no other refuge for sinners than to flee to Christ.