Why is it said of our master Ali, "May God honor his countenance"?

It is obligatory for a Muslim to respect and venerate all the Companions without exception, and to supplicate for Allah's pleasure upon all of them. When any of them is mentioned, one should say: "May Allah be pleased with him (radiyallahu anhu)." The تخصيص (designation) of Ali, may Allah be pleased with him, with the phrase "karrim Allah wajhahu" (may Allah honor his face) or "alaihi al-salam" (upon him be peace) is something that became prevalent in the expressions of some scribes. While its meaning is sound, equality should be observed among the Companions in this regard. Ibn Kathir mentioned that the two Shaykhs (Abu Bakr and Umar) and Uthman are more deserving of such honor. As for the justifications for singling out Ali, none of them are valid. Among these justifications are that he never prostrated to an idol and that he never looked at anyone's private parts, but these characteristics are shared by all Companions who were born into Islam.