The word "so" in John 3:16 is a little one, but who has ever yet been able to sound the depth of its meaning? It is like some of our Lord's "ifs" in John 8, which are full of eternal significance. Let us examine them.
The "If" of Discipleship
"If ye continue in My Word, then are ye My disciples indeed" (John 8:31). True discipleship is the result of abiding in the truth revealed to us in Jesus Christ. Difficulties are sure to arise for those who follow Christ, and many stumble and forsake Him in heart or in practice (Matthew 13:20,21). To not continue in His Word is to forfeit our fellowship with Him, for the soul of Jesus Christ can have no pleasure in the man that draws back from the clear light of His Word (Hebrews 10:38). Peter was a disciple indeed when he boldly preached the Christ whom he once denied.
The "If" of Freedom
"If the Son therefore shall make you free, ye shall be free indeed" (John 8:36). The freedom which the Son of God gives is a freedom that can come from "none other name under heaven." It is freedom from the curse of the law (Galatians 3:10), from the guilt of sin (Romans 8:33), from the power of sin (Romans 6:14), from the fear of death (Hebrews 2:15), and the fear of man (Acts 4:18-20). It is the freedom of sons who have liberty of access into the Father's presence.
The "If" of Service
"If ye were Abraham's children, ye would do the works of Abraham" (John 8:39). "They which are of faith, the same are the children of Abraham" (Galatians 3:7). The spiritual children of Abraham show their faith by their works, as he did. Abraham believed God, and his faith was evidenced by his works when he "went out not knowing whither he went," and when he offered up his son Isaac. Those who are the true children of the "Father of the faithful" will do works worthy of their Father. Works of faith are the natural, inevitable product of true spiritual life (James 2:20-24).
The "If" of Sonship
"If God were your Father ye would love Me" (John 8:42). There is no way to the Father but by the Son (John 14:6). To know the Father, as He is revealed to us in the Son, surely implies that we will sincerely love the Son for bringing us into such a gracious knowledge of the Father. To call God Father, and deny the Son, is to insult both Father and Son. The evidence of our sonship with God is love for His Son. If God is our Father in a true, practical sense, we will not only supremely love the Lord Jesus Christ, but we will also love every child of God, for "Every one that loveth Him that begat, loveth him also that is begotten of Him" (1 John 5:1).
The "If" of Responsibility
"If I say the truth, why do ye not believe Me?" (John 8:46). He spoke the truth, and lived it, for no one was able to "convince Him of sin." He spoke the truth about Himself, about His Father, and about the needs and responsibilities of the people (vv. 12-24). They could not deny the truthfulness of His character or the mercifulness of His mission, yet they did not believe in Him—they did not commit themselves to Him. "Why do ye not believe Me?" Who shall ever be able to justify themselves in their unbelief? Oh, the infinite madness of refusing to believe Him who is the living embodiment of the Eternal Truth! "Why did ye not believe Me" will have an awfully solemn ring about it when the unbeliever meets Him at the judgment throne.
The "If" of Assurance
"If a man keep My saying, he shall never see death" (John 8:51). Eternal life and salvation is in that Word. Death can have no power over that man whose life is hid with Christ in God. To keep His Word is to keep the message Christ brings, and to appropriate it to our own personal needs; it is to wrap ourselves in it as in a garment, and to abide in it. Thus, by keeping it, we are kept by the power of God through faith. The promise is, "He shall never see death." Of course, it does not mean the death of the body that we often see, but that awful death, the eternal penalty of sin and guilt (Romans 6:23). If it is such a blessing not to see it, what a horror it must be to be in it!
—From "Handfuls on Purpose"