Him.
He went on to say: “The tawḥīd that is required is not confined to tawḥīd ar-rubūbiyya—the mere belief that Allah alone created the universe—as some theologians and Sufis imagine. They think that once they establish this through rational proof they have reached the pinnacle of tawḥīd, and that when they contemplate it until they are obliterated in it, they have attained the utmost limit of tawḥīd.
“For if a man were to affirm all the attributes the Lord—exalted is He—deserves, declare Him free of every imperfection, and acknowledge that He alone is the Creator of everything, he would still not be a true monotheist until he bears witness that there is no god but Allah alone; that is, until he acknowledges that Allah alone is the deity entitled to worship and binds himself to worship Allah alone with no partner.
“The ilāh is the One adored and worshipped who deserves worship; ilāh does not mean ‘the One capable of originating creation’. So when someone defines ilāh as ‘the One able to bring things into being’, regards this as the deity’s most exclusive attribute, and makes proving this the goal of tawḥīd—as certain speculative theologians do, attributing the view to Abū al-Ḥasan and his followers—they have failed to grasp the reality of the tawḥīd with which Allah sent His Messenger ﷺ. The pagan Arabs acknowledged that Allah alone is the Creator of everything, yet they were still polytheists. Allah the Exalted has said: “Most of them do not believe in Allah except while they associate others with Him” 1. A group of the early Muslims explained this verse, saying: ask them, ‘Who created the heavens and the earth?’ and they will say, ‘Allah,’ yet they still worship others besides Him!
“Allah, the Exalted, also said: “Say, ‘To whom belongs the earth and all who are in it, if you know?’ They will say, ‘To Allah.’ Say, ‘Will you not then take heed?’ Say, ‘Who is the Lord of the seven heavens and Lord of the mighty Throne?’ They will say, ‘Allah.’ Say, ‘Will you not then fear Him?’ Say, ‘In whose hand is the dominion of all things—He protects while none can protect against Him—if you know?’ They will say, ‘To Allah.’ Say, ‘Then how are you deluded?’” 2.