Daniel Wallace, Revelation 3:20 and the Offer of Salvation.

“What then should we say when we are trying to lead someone to Christ? I think a better picture is simply what the New Testament uses as its normative word – πίστις/πιστεύω. The noun form (πίστις) can be translated “faith,” “belief,” or “trust.” The verb can be translated “I believe,” “I have faith,” “I trust.” In some contexts the object of belief is emphasized (namely, Christ); in other contexts, the kind of belief is emphasized (namely, a genuine trust, an embracing). Thus, πίστις has this twofold force of content and conviction. To be saved, one must have the right object of faith (content); and one must truly put his trust entirely in that object (conviction).”
Daniel Wallace
Revelation 3:20 and the Offer of Salvation.