This is a fantastic verse!
After years of clumsily wandering around the truth that was right there - not just in his midst, but with him most days and most nights... talking, sharing, teaching, reading perhaps and retelling stories of ages past that told of ages future.
The man Jesus, the son of God had called Thomas to be one of the 12! Thomas, like all of us, answered the call, the invitation, to be with Jesus, to trust him, to believe him, to follow him to some amazing, and, some dark, dark places - like us, he had no concept of what his 'yes' would entail or lead to - what it would do to his life - forever on.
Jesus tried to explain - again and again, in many ways, but they all had huge gaps in their understanding and belief. (remember they went fishing after Jesus died, as that was one of the only things they knew was true right then John 21:3)
Jesus told them these truths - they heard the words, but knew not yet what they meant;
Do not let your heart be troubled; believe in God, believe also in Me. John 14:1
v5 Thomas said to Him, “Lord, we do not know where You are going, how do we know the way?” 6 Jesus said to him, “I am the way, and the truth, and the life; no one comes to the Father but through Me.
v7 If you had known Me, you would have known My Father also; from now on you know Him, and have seen Him
v10 The words that I say to you I do not speak on My own initiative, but the Father abiding in Me does His works
16:17 A little while, and you will not see Me; and again a little while, and you will see Me’
v32 I am not alone, because the Father is with Me
20:24 "But Thomas,...said to them, “Unless I see in His hands the imprint of the nails, and put my finger into the place of the nails, and put my hand into His side, I will not believe.”
No one has seen the Father. But in Jesus, who is the image, the likeness, the form of the Father, they got to understand who God was in Jesus - they got to KNOW Him. See 14:7 to 'see', means to know - to understand, to believe, to trust! Not see with the eyes - but know with the heart and soul. To feel the same spirit in God, in Jesus - in them!
Slowly at first, took a big tumble when he died, but when he came back - now the pieces started to fit, the words make sense! This Jesus, who said he was the son of God (wow!), who said he and the Father were ONE! (not one substance or something, but one in purpose and spirit) And Jesus said they should be 'one with him' as he was with the Father.
So Thomas, seeing the proof, feeling the awe and the moment of wonder and truth that no words could ever express - saw his God for the first proper time in and through the man Jesus - the son of God. My Lord Jesus, and my God who you have been showing us - now I see it is all true and very real!
Echoing Job, My ears had heard of you but now my eyes have seen you. Job 42:5
John 14:4 And you know the way where I am going.” 5Thomas said to Him, “Lord, we do not know where You are going, how do we know the way?” 6Jesus said to him, “I am the way, and the truth, and the life; no one comes to the Father but through Me.
Clearly we would understand that Thomas knew from Jesus' words, and from his own understanding, that his God and Jesus were not the same person. Jesus is speaking to Thomas specifically. Thomas already expressed doubt in John 20:25 unless I put my fingers in his hand etc.
Thomas is being prepared for his awakening when Jesus is raised from the dead and Thomas finally gets it. Did Thomas think Jesus raised himself? That's not what Jesus had been teaching them. John 11:23-
As if Thomas would expect his GOD to have nail holes in his hands! Let alone die on a cross and be dead for 3 days!
Thomas addressed two persons - His Lord Jesus, and his God Yahweh.
We can of course take these words and misunderstand what Thomas meant. We might construe it to mean Jesus IS God - as many have done. But to do so is to ignore the repetitive and consistent statements from Jesus who said that he was,
'a man who has told you the truth' John 8:40
who could do nothing of himself - no words, no miracles, unless the Father did it through him.
a lamb sent to die (and was raised by his Father and God)
exalted to the heavens to be with the Father (appointed heir of all things Heb 1:2)
We can ignore the statements from the apostles about Jesus having a God;
1 Pet 1:3 Praise be to the God and Father of our Lord Jesus Christ (Rom 1:7, Eph 1:3, Col 1:3, 2 Cor 1:3, 11:31, Rom 15:6, Acts 2:36
Phil 2:9 Therefore God exalted Him to the highest place and gave Him the name above all names
John 20:17 I ascend to My Father and your Father, and My God and your God.
who clearly understood and taught that Jesus was certainly NOT God, but the glorious son OF God. Or we can stick to a few other verses that seem to say Jesus IS God when we read things into the Word of God that are not supported by the broader narrative.
Even when Jesus is ascended at God's right hand, he still refers to God as 'my God', Rev 1:5-6, 3:2, 12.