Let’s face it – it’s tough for anyone to believe that Jesus could be fully God and Man at the same time. But however hard it might be to understand, we have the best of reasons to believe it’s true. John points to the testimony of the Spirit, the water and the blood. At the time of Jesus’ baptism, the Spirit descended on Him like a dove, as He rose from the waters. And God the Father also spoke about Jesus at the same time, saying from Heaven, “This is My beloved Son, in Whom I am well pleased” (Matthew 3:16-17). No, there can be no doubt that Jesus was truly the Son of God.

Well, what about His humanity? At the end of Jesus’ life, the water and blood also testified to Jesus’ humanity, as both of them poured out of His side when a Roman soldier pierced Him with a spear (John 19:34). Meanwhile, God bore witness as the light of the sun was blotted out for three hours, there was a great earthquake, and the curtain of the Temple was torn in two from top to bottom (Matthew 27:45, 51). We can have no doubt that the Son of Man died on the cross, paying the death penalty all our sins deserve.

So yes, we have every good reason to believe that Jesus was fully God and fully Man at the same time. And it is important for us to believe this. After all, in verse 10, John reminds us that since God has made His identity so clear, if we were to reject the claims of Christ we would be calling God a liar. And verse 12 says that means cutting ourselves off from the only true source of light and life.

But believing in Jesus, trusting Him as Savior and bowing the knee to Him as Lord also brings us great benefits. If Christ is within us we have eternal life (v. 11). Moreover, when we trust in Jesus we not only have all the historical evidence of His identity – because He lives within us in His Holy Spirit, we have the testimony, the certainty of the claims of Christ in our hearts as well (v. 10).

So, let’s believe all these reliable witnesses, and let’s rejoice that the Son of God and the Son of Man has sacrificed Himself so that we might be saved.

I John 5:6-12 (ESV)

6 This is he who came by water and blood– Jesus Christ; not by the water only but by the water and the blood. And the Spirit is the one who testifies, because the Spirit is the truth.
7 For there are three that testify:
8 the Spirit and the water and the blood; and these three agree.
9 If we receive the testimony of men, the testimony of God is greater, for this is the testimony of God that he has borne concerning his Son.
10 Whoever believes in the Son of God has the testimony in himself. Whoever does not believe God has made him a liar, because he has not believed in the testimony that God has borne concerning his Son.
11 And this is the testimony, that God gave us eternal life, and this life is in his Son.
12 Whoever has the Son has life; whoever does not have the Son of God does not have life.