Al-An'am 6:9

Walaw jaAAalnahu malakan lajaAAalnahurajulan walalabasna AAalayhim ma yalbisoon

And if We had made him [i.e., the messenger] an angel, We would have made him [appear as] a man, and We would have covered them with that in which they cover themselves [i.e., confusion and doubt].

If We had made him an angel, We would have obviously made him a man, and would have caused them the same confusion they are causing now.