Where in the old Testament can I find a promise of heaven after death? Is it only after Christ?

I'n not sure what you mean by "promise of heaven after death". Do you mean
1) where in the OT does it say we go to be with the Lord when we die?
or
2) where is Heaven (place) for eternity mentioned in the OT?

You'll have to look for references to the resurrection.

Dan 12:2 And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt.

Job 19:25 For I know that my redeemer liveth, and that he shall stand at the latter day upon the earth:
Job 19:26 And though after my skin worms destroy this body, yet in my flesh shall I see God:
Job 19:27 Whom I shall see for myself, and mine eyes shall behold, and not another; though my reins be consumed within me.

Psa 49:15 But God will redeem my soul from the power of the grave: for he shall receive me. Selah.

Isa 25:8 He will swallow up death in victory; and the Lord GOD will wipe away tears from off all faces; and the rebuke of his people shall he take away from off all the earth: for the LORD hath spoken it.

Where in the old Testament can I find a promise of heaven after death? Is it only after Christ?Here are two references from the Psalms:

Psalm 15:1 Lord, who shall abide in thy tabernacle? who shall dwell in thy holy hill?

2 He that walketh uprightly, and worketh righteousness, and speaketh the truth in his heart.

3 He that backbiteth not with his tongue, nor doeth evil to his neighbour, nor taketh up a reproach against his neighbour.

4 In whose eyes a vile person is contemned; but he honoureth them that fear the LORD. He that sweareth to his own hurt, and changeth not.

5 He that putteth not out his money to usury, nor taketh reward against the innocent. He that doeth these things shall never be moved.


Psalms 24:3 Who shall ascend into the hill of the LORD? or who shall stand in his holy place?

4 He that hath clean hands, and a pure heart; who hath not lifted up his soul unto vanity, nor sworn deceitfully.

5 He shall receive the blessing from the LORD, and righteousness from the God of his salvation.

A few...
Psalms 23:4 Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me; thy rod and thy staff they comfort me. Thou preparest a table before me in the presence of mine enemies: thou anointest my head with oil; my cup runneth over. Surely goodness and mercy shall follow me all the days of my life: and I will dwell in the house of the LORD for ever.

Psalms 30:12 To the end that my glory may sing praise to thee, and not be silent. O LORD my God, I will give thanks unto thee for ever.

Psalms 73:21 Thus my heart was grieved, and I was pricked in my reins. Nevertheless I am continually with thee: thou hast holden me by my right hand. Thou shalt guide me with thy counsel, and afterward receive me to glory. Whom have I in heaven but thee? and there is none upon earth that I desire beside thee. My flesh and my heart faileth: but God is the strength of my heart, and my portion for ever.

Psalms 89:6 For who in the heaven can be compared unto the LORD? who among the sons of the mighty can be likened unto the LORD? God is greatly to be feared in the assembly of the saints, and to be had in reverence of all them that are about him.

Psalms 139:7 Whither shall I go from thy spirit? or whither shall I flee from thy presence? If I ascend up into heaven, thou art there: