The first is the accusative of a second object for prohibition. The second is the nominative of a subject for it. And guidance is revelation, meaning:

What prevented them from believing in the Qur'an and in the prophethood of Muhammad, blessings and peace be upon him, except a doubt that lingered in their hearts, which is their denial that Allah would send humans. The hamzah in 'Aba'atha Allah' is for denial, and what they denied is the opposite of it, which is what is denied by Allah. This is because the matter of His wisdom is that He does not send the angel of revelation except to those like him or to the prophets. Then He confirmed this by saying: 'If there were on the earth angels walking on their feet like humans and not flying with their wings to the sky' [[Mahmoud said: 'Its meaning is if they were walking like humans and not flying with their wings to the sky... etc.' Ahmad said:

And his words contain a good answer to a presumed question, which is the saying of someone: that the mere existence of angels on earth is suitable for sending the angel to them, so what is the benefit of this addition? His answer would be what has preceded, and Allah is the Grantor of success.]] so they would hear from its people and know what must be known, being at peace, settled in the earth. We would have sent down to them from the sky an angel messenger to teach them goodness and guide them to the right path. As for humans, they are not in this position; rather, the angel is sent to a chosen one among them for prophethood, and that chosen one calls them and guides them. If you say: Is it permissible for him to be both a human and an angel, in the accusative as a state of 'messenger'? I say: It is a good aspect, and the meaning has answers.