John 10:30 I and my Father are one.
What this verse doesn’t mean is that Jesus and his Father are one substance, co-equal and co-eternal and of one being. Jesus shows clearly that his Father is superior to (and therefore separate from) himself and knows more than he does.
John 14:28... for my Father is greater than I.
Mark 13:32 But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father.
What it does mean is that Jesus and his Father are united in purpose? Jesus always did the will of God and not his own will. This shows that their wills were distinct and separate and Jesus subjugated his own will to that of God.
John 5:30... I seek not mine own will, but the will of the Father which hath sent me.
Luke 22:42... nevertheless not my will, but thine, be done.
That Jesus and his Father being ‘one’ is limited to a unity of purpose is shown by the prayer of Jesus – that his disciples might be ‘one’ in the same way.
John 17:11... that they may be one, as we are.
John 17:21 That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us... 22... that they may be one, even as we are one:
This can only mean that there was to be no division amongst them in the gospel and doctrine that they would be required to preach for the salvation of others. The converts at Pentecost believed the apostles’ gospel and followed their doctrine.
Acts 2:41 Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.42 And they continued stedfastly in the apostles’ doctrine and fellowship, and in breaking of bread, and in prayers.
1 Corinthians 15:11 Therefore whether it were I or they (the other apostles), so we preach, and so ye believed.
Galatians 1:8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. 9 As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.
1 Corinthians 1:10 Now I beseech you, brethren, by the name of our Lord Jesus Christ, that ye all speak the same thing, and that there be no divisions among you; but that ye be perfectly joined together in the same mind and in the same judgment.
2 Corinthians 13:11... be of one mind, live in peace; and the God of love and peace shall be with you.
1 Timothy 1:3... that thou mightest charge some that they teach no other doctrine,
1 Peter 3:8 Finally, be ye all of one mind...
John 14:1... ye believe in God, believe also in me.
Those that heard the gospel preached by Jesus were required to believe that he was the promised Messiah or Christ. The Jewish leaders refused to believe it. The disciples during his ministry did believe it.
Andrew speaks of Jesus to Peter thus:
John 1:41... We have found the Messias, which is, being interpreted, the Christ.
Peter makes the confession:
Matthew 16:16...Thou art the Christ, the Son of the living God.
Martha makes the same confession
John 11:27... Yea, Lord: I believe that thou art the Christ, the Son of God, which should come into the world.
What the disciples couldn’t understand prior to the death of Jesus was that the Messiah had to die as a sacrifice for sin. When Jesus explained about his crucifixion they found it incomprehensible.
Luke 18:34 And they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken.
After Jesus’ death the perplexity of the disciples is expressed on the road to Emmaus
Luke 24:19... And they said unto him, Concerning Jesus of Nazareth, which was a prophet mighty in deed and word before God and all the people: 20 And how the chief priests and our rulers delivered him to be condemned to death, and have crucified him. 21 But we trusted that it had been he which should have redeemed Israel...
Jesus in John 14:1 is encouraging the apostles to believe in him despite what they would see as their hope, built up over 3.1/2 years of preaching, destroyed by his death.
He explains that he is going (by dying) to prepare a way for them to enter the kingdom of God. His sacrifice (for the remission of sin) was the means whereby they could attain to eternal life.
They could not understand that he had to die and be raised from the dead.
We might conjecture that the disciples pondered on his words in the time between his death and resurrection. When John gets to the sepulchre on the first day of the week and sees the grave clothes lying, the realisation of what Jesus had said seems suddenly to strike him. Prior to any report of Jesus being seen alive, John finally understands and believes in Jesus.
John 20:8 Then went in also that other disciple, which came first to the sepulchre, and he saw, and believed
Thomas was not of the same mindset as John but the resolving of his unbelief serves as positive confirmation; that we in our day might believe in Jesus.
John 20:25... Except I shall see in his hands the print of the nails, and put my finger into the print of the nails, and thrust my hand into his side, I will not believe...
John 20:29 Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.
I hope you have found this helpful.
God bless you,