John 1:45

Philip then brought his friend Nathanael (meaning "God has given" or "given of God," modern Theodore) to Jesus. Some commentators identify Nathanael with Bartholomew (cf. Matthew 10:3; Mark 3:18; Luke 6:14). However there is no convincing reason to equate these two men. The witness continued to spread through the most normal lines of communication, namely, friend to friend, as it still does.

The prophecies to which Philip referred may have included Deuteronomy 18:15-19; Isaiah 53; Daniel 7:13; Micah 5:2; and Zechariah 9:9. These and others spoke of the Messiah. This suggests that the early disciples understood messiahship in the light of the Old Testament background rather than only in a political sense. [Note: Harris, p. 188.] Philip described Jesus as Joseph’s son, which is how people knew Him before they learned that He was the Son of God (John 1:49).

"In one sense it is legitimate to view Jesus’ disciples in the gospel of John (with the exception of Judas Iscariot) as believers in Him from near the beginning of His public ministry. In another sense, however, it is also clear that the disciples’ faith in Jesus grew and developed as they observed the progress of His public ministry. The course of this development may be traced in the gospel of John." [Note: Ibid., p. 215.]