I've notice they couldn't Psalms 2:7:
"All things have been committed to me by my Father. No one knows who the Son is except the Father, and no one knows who the Father is except the Son and those to whom the Son chooses to reveal him." Luke 10:22
Just as the Father is incomprehensible so is his Son, and just as no one completely knows the Son except the Father in a similar manner no one comprehensively knows the Father except his Son!
Because we know that Jesus claimed to be THE Son of God the OT tells us how to treat him:
Serve the LORD with fear, And rejoice with trembling. Kiss the Son, lest He be angry, And you perish in the way, When His wrath is kindled but a little. Blessed are all those who put their trust in Him. Psalms 2:11-12
In Psalm 2 we have a prophetic picture which should be read in its entirety. In vv. 2-3 it describes the time when the nations will stand against God and against his Anointed One (Mashiho, from which our English word Messiah comes). God says in verse 6 that he will nevertheless establish this Messiah as his King on Zion, his holy hill:
Why have nations tumultuously assembled? And do peoples meditate vanity? Station themselves do kings of the earth, And princes have been united together, Against Jehovah, AND AGAINST HIS MESSIAH (Mashiho): `Let us draw off Their cords, And cast from us Their thick bands.' He who is sitting in the heavens doth laugh, The Lord doth mock at them. Then doth He speak unto them in His anger, And in His wrath He doth trouble them: `And I -- I have anointed My King, Upon Zion -- My holy hill.' I declare concerning a statute: Jehovah said unto me, `My Son Thou [art], I to-day have brought thee forth. Ask of Me and I give nations -- thy inheritance, And thy possession -- the ends of earth. Psalms 2:1-8 YLT
In verse 7 Messiah steps forward to declare the decree by which his coronation shall be accomplished, saying: "I will proclaim the decree of the Lord: ‘He said to me, "You are my Son; today I have become your Father. Ask of me, and I will make the nations (goyim) your inheritance."'"
Furthermore, in Psalm 2:11-12 we are solemnly instructed to:
Serve the LORD with fear, And rejoice with trembling. KISS THE SON (nashqu bar), lest He be angry, And you perish in the way, When His wrath is kindled but a little. Blessed are all those who put their trust in Him. Psalms 2:11-12
The Hebrew for "kiss the Son" is nashqu bar. Even if this is translated, as some would have it, "Do homage in purity," the homage is to the Lord of verse 2 and to the Son of verse 7. The Tanakh (Hebrew Bible) clearly indicates that there is a Divine personality who is called the Son of God!
Some Muslims have attempted to link this passage, particularly Psalms 2:7, to David; however this is easily refuted since neither the Holy Bible nor the Quran calls David the Messiah nor does either one claim that one must put their trust in David. Hence, to call David "the Son" in this verse would refute all of Islam and the Quran because this passage explicitly refers to THE MESSIAH, who is Jesus according to Islam!
