Trevor Stewart-Sweet
Isaiah begins by declaring in verse 1, he says,
O Lord, You are my God.
Isaiah 25.1
I will exalt You,
I will praise Your name,
For You have done wonderful things;
Your counsels of old are faithfulness and truth.
Isaiah begins by acknowledging that the Lord is his God. The Lord, as he puts it, is my God, the only God whom Isaiah exalts, and the only Name whom Isaiah praises.

God’s Name (Jewish people always refer to God as Hashem, the name), God’s Name is Jehovah represented in scripture as the tetragrammaton YHWH

‘Yahweh’ or, as in many Bibles (mine included) where you see ‘LORD’ written in capital letters.
So verse 1 begins: Oh Jehovah Thou Art my God.
Isaiah addresses God by his personal name ‘Jehovah’. If we go back to chapter 12 we can see there that Isaiah acknowledged God where he said in verse 2,
Behold, God is my salvation,
Isaiah 12.2
I will trust and not be afraid;
‘For Yah, the Lord, is my strength and song;
He also has become my salvation.’
We sing that sometimes, don’t we? The Lord my God is my strength and my song, He also has become my salvation.
In this particular verse of chapter 12, Isaiah mentions five things that he knows of God.
Firstly, he said God is my salvation. The Hebrew there is יְשׁוּעָתִ֛י Yeshuati (yǝšûʿātî): God is my salvation, and he has become my salvation. There is that word yǝšûʿā Yeshua יְשׁוּעָה.

You see, Isaiah knows that God is his salvation. Here, the context is ‘salvation from Israel’s enemies’, but we can also understand that the Hebrew word for salvation is the Hebrew name of Jesus / Yeshua יְשׁוּעָה.
I’m not sure if you’ve ever looked this up but there are 78 instances of Yeshua in its various forms in 77 verses of the Hebrew scriptures. 49 of those are in the Psalms. And Isaiah mentions Yeshua or uses the term Yeshua 19 times in 18 verses.

And here, we can see that God, in this verse, Lord and Yeshua יְשׁוּעָה / Yeshuati יְשׁוּעָתִ֛י my salvation, God, and Yeshua are one and the same.
God is my salvation. Yeshua / Jesus is the only source of Salvation. He is the only one who has the victory over the power of sin and death.

There’s no doubt that Isaiah knew God and had implicit faith in God, and you know one day we shall see Isaiah in glory, amen.