The expression to believe in [Jesus’] name occurs five times in the New Testament, all in the Johannine literature. The expression πιστεύω εἰς τὸ ὄνομα αὐτοῦ to believe in his name occurs in John 1:12; 2:23; πιστεύω τῷ ὀνόματι τοῦ υἱοῦ αὐτοῦ ’Iησοῦ Xριστοῦ to believe in the name of his Son, Jesus Christ in 1 John 3:23; πιστεύω εἰς τὸ ὄνομα τοῦ υἱοῦ τοῦ θεοῦ to believe in the name of the Son of God in 1 John 5:13; and πιστεύω εἰς τὸ ὄνομα τοῦ μονογενοῦς υἱοῦ τοῦ θεοῦ to believe in the name of the unique Son of God in John 3:18. But what does it mean to believe in Jesus’ name?
When John advocates believing in the name of Jesus, it is handy to substitute the word title for name. To believe in Jesus’ name is to acknowledge Jesus’ title, to acknowledge who Jesus really is, and in particular, to acknowledge who Jesus claimed to be, i.e., to accept the truth that Jesus is the Christ, the anointed one, the Son of God, the divinely-chosen divine King of salvation.
For John, Jesus’ name or title is twofold. Firstly, Jesus is the Christ; and secondly, Jesus is the Son of God (see John 20:31). These terms are virtual synonyms in John’s usage, although the term the Son of God also implies (for John) that Jesus is divine. This twofold understanding of Jesus’ name can be seen from the terms used by John in connection with the idea of Jesus’ name. In John 1:12, believing in Jesus’ name is paralleled with receiving him. In John 2:23, many people believe in Jesus’ name after seeing the many signs that Jesus performed. The signs presumably convinced them that Jesus was the Christ. In 1 John 3:23, the terms Christ and [God’s] Son are used. In John 3:18 and 1 John 5:13, the term the Son of God is used.
Thus, to believe in Jesus’ name is to confess that Jesus of Nazareth is the Christ, the Son of God.
