John 10:28-39
28 And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.
29 My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand.
30 I and my Father are one.
31 Then the Jews took up stones again to stone him.
32 Jesus answered them, Many good works have I shewed you from my Father; for which of those works do ye stone me?
33 The Jews answered him, saying, For a good work we stone thee not; but for blasphemy; and because that thou, being a man, makest thyself God.
34 Jesus answered them, Is it not written in your law, I said, Ye are gods?
35 If he called them gods, unto whom the word of God came, and the scripture cannot be broken;
36 Say ye of him, whom the Father hath sanctified, and sent into the world, Thou blasphemest; because I said, I am the Son of God?
37 If I do not the works of my Father, believe me not.
38 But if I do, though ye believe not me, believe the works: that ye may know, and believe, that the Father is in me, and I in him.
39 Therefore they sought again to take him: but he escaped out of their hand,
Jesus says that "I and my Father are one", and the Jews go to stone Him for blasphemy, saying, "that you, being a man, make yourself God" (John 10:33).
Jesus statement that "I and my Father are one" is not an ontological statement that they have the same Essence, as it was construed by some early and Medieval Christians. That interpretation, since the advent of historical-grammatical hermeneutics, has largely been discarded by modern Trinitarian advocates.
Later in the same book, Jesus prays to the Father, and in reference to believers, asks "that they may be one, even as we are one":
John 17:11, 22-23
11 And now I am no more in the world, but these are in the world, and I come to thee. Holy Father, keep through thine own name those whom thou hast given me, that they may be one, as we are.
22 And the glory which thou gavest me I have given them; that they may be one, even as we are one:
23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
Above, John has Jesus say that He wants believers to be "one" in the same way that He is "one" with the Father. This demonstrates that it is a severe over-reading to attempt to turn John 10:30 into a statement about the ontology of God. It simply states that Jesus and His Father are in agreement, or united in purpose and mission (see 1 Corinthians 3:8), and while there are many senses in which this could be said to be true, the immediate context is their united resolve not to lose any believers (John 10:28-29).
In regard to the hostile Jews accusing Him of blasphemy, saying, "you, being a man, make yourself God" (John 10:33), one should immediately be careful when dealing with the words of spectators in the Gospels, especially hostile ones, as they are frequently wrong, or missing the point (Matthew 13:54-58, Mark 3:21-22, Luke 7:39, 23:35-39, etc.).
Jesus responds to their accusation, in which He in essence says that even human beings can be called "God", and yet, He actually said that He was "the Son of God" (John 10:34-36). But, it is extremely unlikely that the Jews meant to accuse Him of literally claiming to be God. Instead, they were almost certainly accusing of usurping the honor, privileges, and prerogatives which they deemed to be off-limits for human beings, just as in John 5:16-18, wherein they think something similar when Jesus claims the right to determine what work is appropriate for Himself on the Sabbath. Jesus corrects them, in this passage - they are wrong, and the Messiah can do more than they think He should be able to do.