Updated: Jan 1
By Luke Lancaster
Many of our Protestant brothers and sisters will attempt to prove their doctrine of Sola Fide by quoting this famous text from Scripture, "For God so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life." This verse is rich in explaining how we are saved by our faith in Christ, but "faith" does not mean a purely mental belief.
Faith is both interior and exterior, not one or the other. The Greek word for "faith" is "pistis," which can be translated EITHER as "faith" or as "faithfulness" (Strong's Concordance). This understanding of faith is actually implied later on in John 3, where it says, "He who believes in the Son has eternal life; he who does not obey the Son shall not see life" (John 3:36). Believing is synonymous with obeying.
Let's also realize that Vines' Greek New Testament Dictionary says that “believe” means three things: to trust in God, to rely on God, and to obey God. "Obeying God" would refer to things such as: good works (John 3:36, 5:29), repentance (Acts 2:38), baptism (John 3:5, 1 Peter 3:21), Eucharist (John 6:53), striving for holiness (Hebrews 12:14), avoiding serious sin (John 5:29, 1 Cor. 6:9-10), providing for relatives and family (1 Timothy 5:8), helping other people in need (Matt. 25:31-46), etc. Without these things, you do not have faith that will give eternal life, for faith leads to actions.
Another key point to consider is how John 3:16 says that those who believe "will have" eternal life - which is in the future tense. This is not a one-time only, "accept Jesus into your heart and you will be saved" moment. We have to live entire lives with faith, and only then will we receive "eternal life."
Protestants try to divorce faith from good works still, and they attempt to use John 3:16. But, their attempt is futile.