The prohibition is borrowed to refrain from sending the signs due to the diversion of wisdom. The first 'that' is in the accusative case and the second is in the nominative case, its meaning being: And what prevented us from sending the signs except the denial of the former peoples. What is meant are the signs that Quraysh proposed, such as turning the rock of Safa into gold and reviving the dead, among others. And Allah's custom with nations is that whoever among them proposes a sign and is answered, then does not believe, is hastened with the punishment of annihilation. So the meaning is: And what diverted us from sending what they propose of signs is only that those who are like them, whose hearts are sealed, such as 'Aad and Thamud, denied them. And if they were sent, they would deny them just as those did and say this is clear magic, just as they say about others, and they would deserve the total punishment. We have decided to postpone the matter of those to whom you were sent until the Day of Resurrection. Then he mentioned one of those signs that the former peoples proposed and then denied when it was sent, and they were destroyed: it is the she-camel of Salih, because the traces of their destruction in the lands of the Arabs are close to their borders, visible to those who come and go, clearly seen. It is read: 'mubṣirah' with an open 'm' so they wronged themselves by it and disbelieved in it. And what we send with the signs, if he intends by it the proposed signs, the meaning is that we do not send them except as a warning of the imminent punishment, like a precursor and an introduction to it. If they do not fear, it will befall them. And if he intended something else, the meaning is: And what we send of the signs like the signs of the Qur'an and others is only as a warning and a forewarning of the punishment of the Hereafter.