Imam al-Hadi (peace be upon him): Allah the Mighty and Majestic has informed of His preferring the children of Adam over the rest of His creation — the cattle, the beasts of prey, the creatures of the sea, the birds, and every moving creature that the senses of the children of Adam can perceive — by the distinction of intellect and speech. And this is His saying: "Indeed We created man in the best of stature" (Tin/4), and these verses: يا أَیُّهَا الْإِنْسانُ ما غَرَّکَ بِرَبِّکَ الْکَرِیمِ * الَّذِی خَلَقَکَ فَسَوَّاکَ فَعَدَلَکَ [O man! What has beguiled you from your Lord, the Gracious one, who created you, then made you complete, then made you symmetrical], and likewise it has come in many other verses. So the first blessing of Allah upon man is "a sound intellect" and his being preferred over many of the other creations because of possessing a complete intellect and eloquent speech. This is because every moving creature on the surface of the earth stands by its own senses and moves toward its own perfection, and He has preferred man because of speech, which does not exist in the other creations. It is by means of speech that Allah has given man dominance over the rest of the creations, to the point that he became one who commands and forbids, and others are subjected to him. He is the One who subjected the sea [to you] so that you may eat fresh meat from it and extract from it ornaments to wear [such as pearls] (Nahl/14). And this verse: "And He created the cattle for you; in them there is warmth [clothing] and [other] benefits, and from them you eat! And there is beauty and splendor for you in them when you bring them back to their resting place, and when [in the morning] you send them out to pasture! They carry your heavy loads to a city which you could not reach except with great hardship" (Nahl/5-7). So for this reason Allah has called man to follow His command and to obey Him, since He has given him preference and precedence by means of well-proportioned creation and by granting complete understanding and knowledge, after He had bestowed upon them the ability to carry out the obligations. And on the other hand, He has made hajj and zakat obligatory upon the wealthy, because He has given him the capacity and ability to perform them, and He has exempted the poor from paying zakat and performing hajj.