Ecclesiastes 9:5 For the living know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten.
OR, from 1 Corinthians 15:
"...if Christ has not been raised, your faith is vain...Then those who have fallen asleep in Christ have perished."
Is Jesus dead or alive? Are the believers in Christ who have gone before us dead, or alive in Christ?
The Old Testament portrays the destination of those who have departed this earthly life as Sheol, Hebrew for the "abode of the dead," a comfortless place, where both the good and the evil live a shadowy existence like wraiths, in silence and oblivion, with neither reward nor punishment.
In the quote you cited from Ecclesiates, there seems to be no afterlife destination at all, but merely "the grave". The Book of Ecclesiates continues, "Whatever your hand finds to do, do it with all your might, for in the grave [Sheol], where you are going, there is neither working nor planning nor knowledge nor wisdom." (Ecc. 9:5-10, NIV)
You can see from many, many OT references to Sheol, that there was not yet a revelation from God about the gift of Eternal Life. I'm just copying the following from an on-line concordance, so you can check it out fo yourself:
Genesis 37:33-35; Genesis 42:37-38; Genesis 44:27-31; Numbers 16:23-33; Deuteronomy 32:22; 1 Samuel 2:6; 2 Samuel 22:5-6; 1 Kings 2:6; 1 Kings 2:9; Job 7:9-10; Job 11:7-8; Job 14:11-14; Job 17:13-16; Job 21:13; Job 24:19; Job 26:6; Psalms 6:5; Psalms 9:17; Psalms 16:10; Psalms 18:4-5; Psalms 30:3; Psalms 31:17; Psalms 49:14-15; Psalms 55:15; Psalms 86:13; Psalms 88:3; Psalms 89:48; Psalms 116:3; Psalms 139:8; Psalms 141:7; Proverbs 1:11-12; Proverbs 5:5; Proverbs 7:27; Proverbs 9:18; Proverbs 15:11; Proverbs 15:24; Proverbs 23:14; Proverbs 27:20; Proverbs 30:16; Ecclesiastes 9:10; Isaiah 5:14; Isaiah 7:11; Isaiah 14:11; Isaiah 14:15; Isaiah 28:15; Isaiah 28:18; Isaiah 38:10; Isaiah 38:18; Isaiah 57:9; Ezekiel 31:15-17; Ezekiel 32:21; Ezekiel 32:27; Hosea 13:14; Amos 9:2; Jonah 2:2; Habbakuk 2:5
My point is, it wasn't until Jesus lived, died, and rose again for our salvation, that the Church received the fullness of the revelation about Eternal Life.
As far as the Old Testament people knew, the grave was The End. St. Paul says, "If Christ was not raised...those who have fallen asleep in Christ are the deadest of the dead." (1 Cor. 16-17)
I believe in the Resurrection. And I believe that those believers in Christ who have departed this earthly life are alive in Christ.