Isaiah 8:19
19 When men tell you to consult mediums and spiritists, who whisper and mutter, should not a people inquire of their God? Why consult the dead on behalf of the living?
Evidence of a belief in life after death. Maybe. Or at least acknowledgement that the dead can be communicated with? The spiritualists and mediums were practitioners of other religions in the surrounding areas, so perhaps Isaiah is instead mocking this by saying in a sarcastic tone, “Why should the living consult the dead? After all, they dead have nothing to say, since they’re dead.” That could be, and it shows evidence that the idea at least existed culturally that some groups believed that there was something after death. This still isn’t the heaven/hell/reward/punishment structure that we have, though.