Our spirit returns to God, where it come from. He gave us the breath of life [spirit] and He takes it back to Him upon our death.
Psalm 31:5 "Into your hands I commit my spirit; redeem me, O LORD, the God of truth."
Jesus knew this.
Luke 23:46 "Jesus called out with a loud voice, "Father, into your hands I commit my spirit." When he had said this, he breathed his last."