The one and only condition to be eternally saved is to believe. To believe means to be persuaded that something is true (see here). If you believe the saving message is true, then you are saved. There is nothing more for you to do. “Most assuredly, I say to you, he who believes in Me has everlasting life,” Jesus said (John 6:47 NKJV).
Although the only condition of salvation is to believe, like any good writer, the authors of the NT would use metaphors and illustrations and synonyms for faith. But they do not intend you to conclude that those are additional conditions of salvation. For example, John wrote:
But as many as received Him, to them He gave the right to become children of God, to those who believe in His name (John 1:12).
John is using “receiving” as a metaphor for faith. Believing in Jesus is like receiving someone. But John does not mean that you must do two things to be saved: believe and receive.
However, it sometimes happens that modern evangelists take these metaphors, illustrations, or synonyms and present them as additional conditions of salvation. The way they evangelize makes it seem like you must believe plus do these other things. And when that happens, the saving message gets garbled or lost entirely.
For example, here is an excerpt from a book on God’s saving purpose. These quotations come from a single page in that book:
“The gospel is the truth that whoever calls upon the name of the Lord (by seeking Him in faith) will be saved…
“No one has ever been saved outside of the gospel, for “it is the power of God for salvation to all who believe” (Rom 1:16-17). The gospel calls all to repent and trust in the Lord for salvation…
“Whoever repents and trusts in the Lord for their salvation and calls upon His name in faith is forgiven and credited with righteousness, being set apart in the Son…
“Salvation comes by hearing and trusting the gospel, the news of God’s goodness and provision…”
Here are all the conditions that were presented as necessary for salvation:
Maybe the author thinks that words like trusting and repenting are synonyms for faith and that “calling upon the Lord” is a metaphor for faith. He might hold that the only condition of salvation is to believe. If so, is that what comes across in his presentation? Does his evangelism communicate a faith-alone message?
Not at all.
Imagine if you were an unbeliever who has just heard this evangelistic message. Would it be clear to you what you must do to be saved? Or do you think you might be a little confused?
I think people would be confused.
I think they would conclude that believing is not enough. The person hearing this presentation would think that he must believe to be saved, but that believing by itself is not enough—trusting, repenting, and calling upon the Lord are also required.
No evangelist wants to be confusing. So here’s a general principle: avoid presenting metaphors, synonyms, or illustrations for faith as if they were additional conditions of salvation.
By all means, use other words to explain or illustrate what it means to believe. But make sure to say you are not giving two or more conditions of salvation but explaining the one condition. And if in doubt, leave the metaphors, synonyms, and illustrations out.