while believing that venerating this created being is less than venerating Allah, yet he swears by it out of veneration for it; likewise, slight showing off, and similar well-known matters. Such things do not fall under disbelief—unless it is said that they are disbelief lesser than disbelief. In any case, they do not fall within what the author means here, for what he intends here is shirk that constitutes apostasy, and this can only be major shirk.
If a person associates partners with Allah, he is a disbeliever in a sense that expels one from the religion, whether this is through belief, speech, or action.
As for belief, it is to believe that Allah, Exalted is He, has a partner in creation, governance, dominion, worship, or anything similar.
As for action, an example is prostrating to an idol.
As for speech, an example is to supplicate someone besides Allah, seek his aid, or say: “Here I am; You have no partner, except a partner who belongs to You; You possess him and all that he possesses,” and similar statements.
Thus, associating partners with Allah—whether in the heart, in speech, or in action—is considered apostasy from Islam. Associating partners with Allah also includes associating someone else with Him in legislation: namely, believing that someone other than Allah has the right to enact laws for people and to put them in place of Allah’s law. Allah the Exalted says:
“They have taken their rabbis and monks as lords besides Allah, and the Messiah, son of Mary; though they were commanded only to worship one God.” [al-Tawbah 9:31]
They would declare lawful what Allah had forbidden, and so they would regard it as lawful; and they would declare forbidden what Allah had made lawful, and so they would regard it as forbidden. As for the one who enacts such laws, he has placed himself in the position of divinity or lordship—that is, he has made himself a lord who legislates. Whoever obeys him in this and agrees with him is a polytheist, because he has placed him in the rank of a lord with regard to legislation.