Why did Jesus' disciples believe in him after he turned water into wine?

Question

Yeshu'a did this beginning of the signs in Kana of Galil, and he manifested his glory, and his disciples believed in him. (John 2:11)

What were these "signs" a sign/ indication of?

Answer 1

Although I heartily agree with the spirit of the answers already given, I think it is important to explore what John himself had in mind when he penned the words in question. When you take a look at some of the other usages of "sign" in John's gospel (and there are several), a pattern emerges. Here is a sampling:

John 2:18

The Jews then said to Him, “ What sign do You show us as your authority for doing these things?” ^{(italics added)}

John 2:23

Now when He was in Jerusalem at the Passover, during the feast, many believed in His name, observing His signs which He was doing. ^{(italics added)}

John 3:2

this man came to Jesus by night and said to Him, “ Rabbi, we know that You have come from God as a teacher; for no one can do these signs that You do unless God is with him.” ^{(italics added)}

John 4:48

So Jesus said to him, “Unless you people see signs and wonders, you simply will not believe.”

John 6:14

Therefore when the people saw the sign which He had performed, they said, “This is truly the Prophet who is to come into the world.” ^{(italics added)}

That final reference is probably the clearest. The signs were intended to confirm Jesus' identity as the Messianic Prophet, sent by God, as foretold in Deut 18 and elsewhere. (This perhaps echoes the idea found in Deut 13:1 that prophets are confirmed by both signs/wonders AND a Biblical message.)

[Note: That the people (or even the disciples) understood that He was, in fact, God incarnate is less certain. His divine identity unfolds gradually for most observers in John's gospel. Consider Thomas for example - Jn 20:28.]

Answer 2

Simply put the 'signs' of Christ were those miracles that manifested his divinity. They were 'pointers' to his divinity and nature of ministry acting as sign posts of authority and seals of divinity. The miracle, or sign, of changing water into wine was the first of his ministry of which there were many afterwards. His signs manifested not just the divinity but the glory of his person and ministry as meek, mild, compassionate, empathetic healer and savior who sanctified and restored all of life as a humble servant and Son of Man on a cross.

This is quite unlike most miracles in the Old Testament which were often a miraculous destruction of sinners. This was 'new wine' in a new covenant that promised better things. Right from the outset Jesus seems much different from John the Baptists, the last of the Old Testament prophets, for John, on his peculiar ministry would not even drink wine and it does not seem like his ministry would tolerate any eating or drinking at a wedding.

This 'sign' which manifested his unique glory, divinity and humble purpose was striking and naturally believed by his true disciples. It was entirely consistent with everything the gospel proclaims - God's manifested kindness and grace in Christ.

Answer 3

Miracles are the ”works” the Father gives to the Son to do, to provide proof that His teachings, ”words” are true. The miracles convince the disciples that Jesus is to be believed. Nicodemus is clear that  no one could do the works Jesus did unless the Father was with him.

Look at soldarnal's answer at Who does Jesus refer to by the phrase “another who testifies about me” in John 5:32?

Quote

So when we get to verse 31 where Jesus claims that his testimony is not valid if he testifies about himself, it again has to do with his relationship to the Father. If the Father is not also testifying about Jesus, then Jesus' own testimony about himself is not valid. But Jesus offers here (as throughout the gospel) the fact of the works (perhaps chiefly, but not limited to, the signs) he has received from the Father (verse 36). Thus the Father testifies about the Son by giving the Son works, which the Son does.

This should give us food for thought here:

Ephesians 2:10 NET For we are his workmanship, having been created in Christ Jesus for good works that God prepared beforehand so we may do them.

and here:

James 2:26 NET For just as the body without the spirit is dead, so also faith without works is dead.