Luke 16:27-31

"'Then he said, "I beg you therefore, father, that you would send him to my father's house".'"

"'"For I have five brothers, that he may testify to them, lest they also come to this place of torment".'"

"'Abraham said to him, "They have Moses and the prophets; let them hear them".'"

"'And he said, "No, father Abraham; but if one goes to them from the dead, they will repent".'"

"'But he said to him, "If they do not hear Moses and the prophets, neither will they be persuaded though one rise from the dead".'"

(And many unbelievers and even some believers ask why God can't just send them a sign from Heaven to prove He's there. Well, because if they refuse to listen to all the signs here on earth, not even a heavenly sign would persuade them; even if it was presented by God Himself.)