Contradiction with Matthew 22:32
Jesus states that God is the God of the living, not the dead, which contrasts with the idea of a particular concern for those who are asleep (i.e., dead).
Matthew 22:32: And when the multitude heard [this], they were astonished at his doctrine.
Contradiction with Ecclesiastes 9:5
This verse claims that the dead know nothing, whereas 1 Thessalonians 4:13 suggests that the living should not be ignorant about those who have died.
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.
Contradiction with John 11:25-26
Jesus speaks of believers never dying, which could contradict the notion of believers needing not to sorrow as others do for the dead.
John 11:25-26: Jesus said unto her, I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live:
Contradiction with Isaiah 26:14
This verse suggests that the dead will not live or rise, differing from the hope of resurrection implied in 1 Thessalonians 4:13.
Isaiah 26:14: [They are] dead, they shall not live; [they are] deceased, they shall not rise: therefore hast thou visited and destroyed them, and made all their memory to perish.
Contradiction with Job 7:9-10
States that those who die will not return to their homes, contrasting the implication of resurrection hope.
Job 7:9-10: [As] the cloud is consumed and vanisheth away: so he that goeth down to the grave shall come up no [more].