“He has ruled and decreed,” is referring to what testimony entails, for ruling and decreeing involve imposing an obligation and issuing a command.

There is no doubt that Allah has made monotheism obligatory upon His creation, commanded them to uphold it, and decreed and ruled accordingly. He says:

“And your Lord has decreed that you worship none but Him.”

He also says:

“Warn that there is no deity except Me, so fear Me.”

And:

“We certainly sent a messenger to every nation, saying, ‘Worship Allah and shun false gods’”—to the end of the verse.

Allah Most High also says:

“Allah has said, ‘Do not take two gods. He is only One God, so fear Me alone.’”

And:

“They were commanded only to worship one God. There is no deity worthy of worship except Him. Exalted is He above whatever they associate with Him.”

“They were commanded only to worship Allah with sincere devotion to Him, inclining to the truth.”

Such passages are numerous in the Quran: He obliges His servants to worship Him alone and forbids them to worship anything besides Him. He has thus ruled and decreed that there is no deity worthy of worship except Him. The question, however, concerns whether the word “testimony” conveys this meaning.

When He testifies that there is no deity worthy of worship except Him, He has declared, explained, and made known that nothing besides Him is a deity and therefore must not be worshipped, and that He alone is the deity who deserves worship. This entails commanding that He be worshipped and forbidding the worship of anything besides Him. For negation and affirmation in such a context entail a command and a prohibition. For example, if someone asks another person for a religious ruling, and someone says to him, “This man is not a mufti; that man is the mufti,” this entails forbidding him to seek a ruling from the former, and commanding and directing him to seek one from the latter.