Jews for Jesus: Is the Trinity in the Hebrew Scriptures?
Logos: The Jewish Trinity and Why the Old Testament Is a Bridge to Faith
One for Israel: THE TRINITY: EASY AS 1, 2, 3?

“Come ye near unto Me, hear ye this:
From the beginning I have not spoken in secret;
from the time that it was, there am I;
and now the Lord GOD has sent me, and His Spirit.”
(Isaiah 48:16)

“Sing and rejoice, O daughter of Zion, for behold, I come and I will dwell in your midst, declares the Lord.
And many nations shall join themselves to the Lord in that day, and shall be my people.
And I will dwell in your midst, and you shall know that the Lord of hosts has sent me to you.”
(Zechariah 2:10-11)