JOHN 2:21-23 NKJV

But He was speaking of the temple of His body. Therefore, when He had risen from the dead, His disciples remembered that He had said this to them; and they believed the Scripture and the word which Jesus had said.

Now when He was in Jerusalem at the Passover, during the feast, many believed in His name when they saw the signs which He did.

JOHN 2:21-23 NKJV

John 2:21, 22 The disciples understood that Jesus was the Messiah (v. 17; 1:41, 45, 49), but they did not understand that He was speaking of the resurrection of His body until it actually happened.

John 2:23 many believed in His name: John’s purpose in recording Jesus’ miracles was for people to believe and have eternal life (20:30, 31). Many have concluded that though the text says these people believed, they did not have true faith. Inasmuch as their faith was only based on Christ’s miracles, they say it was not saving faith. Furthermore, they note that Christ did not commit Himself to them (v. 24); however, John says he recorded the miracles of Christ so that people would believe and have eternal life (20:30, 31). Also the text says they “believed in,” a construction that everywhere else in the NT indicates saving faith. Moreover, they believed in His name, a phrase only used two other times in the Gospel of John and in both places it is of saving faith (John 1:12; 3:18).