'There Is No God But Me'

S 16:2 He sends down the angels with the spirit of his command upon whom he wills of his slaves: Warn that there is no god but me so fear.

As the verse begins in the third person, how might we know that the last sentence isn't the author referring to himself as a god?

S 20:14  I am Allah. There is no god but me. So worship me and perform salat for my dhikr.

This is part of a story in which Allah speaks to Musa, making a claim. Isn't a dhikr a book? Where does prayer come in?

People of the Dhikr

Dhikr

S 21:25 And we did not send before you any messenger but we inspire him: There is no god but me so worship.

So, no messenger was sent by the anonymous speaker/s but he/they inspire/s (present tense) him.