The Old Testament generally uses the word JHWH when referring to one member of the Trinity. This proper name for God or Lord, called the Tetragrammaton, “four letters”, is considered sacred and is never pronounced by devout Jews. We translate JHWH as Jehovah or Yahweh.
Actually, this word is the doubling of the verb “to be,” meaning “absolute existence.”
The context of Scripture may indicate which member of the Trinity the Tetragrammaton describes. For example, the appearance of Yahweh to man, a theophany of the Old Testament, always refers to the Son, the manifest person of the Trinity, John 6:46; cf., John 14:9-10; Isa. 6; cf., John 12:39-41.
Occasionally, Yahweh implies all three persons, as in the general blessing,
“The Lord [Yahweh] bless you, and keep you; the Lord make His face shine on you, and be gracious to you. The Lord lift up His countenance on you, and give you peace.”, Num. 6:24-26.
Another Old Testament reference to the Trinity is in the pronoun “us.” God again refers to Himself in the plural.
Then God [Elohim] said, “Let Us make man in Our image…,” Gen. 1:26a, 27a.
While these words imply a heavenly convocation among the members of the Godhead, a decision-making process within, the Trinity, there has never been a time when omniscient God did not know all that is, knowable. God cannot be indecisive; rather He mandates from His infinite and eternal knowledge.
Then, He communicated to us in a form of expression we could fathom. He described His indescribable person and plan in terms of human experience. His language accommodated our limited ability to comprehend the infinite. Thus, human beings can understand what God set forth in the divine decree. Such biblically recorded “convocations” among the members of the Trinity serve to verify the existence of the three-fold personality of God, Gen. 3:22; 11:7; Isa. 6:8.
Gen 3:22 And the LORD God said, Behold, the man is become as one of us, …
Gen 11:7 Go to, let us go down, and there confound their language, …
Isa 6:8 Also I heard the voice of the Lord, saying, Whom shall I send, and who will go for us?