Al-An'am · 6:28

28. Their saying that they would believe if sent back is a lie. Instead the statement that they used to keep hidden, which was ‘By Allah, we were not idolaters,’ has appeared to them when their limbs gave testimony against them. If they were supposedly sent back to the world, they would return to the disbelief and associating partners with Allah that they had been prohibited from. So they are lying in their promise that they will believe if they are sent back.