The fourth pinciple of faith printed in the siddur is
אני מאמין שהבורא יתברך שמו הוא ראשון והוא אחרון
I believe with a complete faith that the Creator is first and last.
However, if we compare this to the source in the Rambam's Peirush Hamishnayos we will see that he DIDN'T say that [even though it is based on a pasuk in Yeshayahu]. The principle is JUST that Hashem was first and that nothing preceded him.
The addendum of Hashem also being last removes the emphasis on His being first. The Ramabm in Hilchos Teshuva [3/7] says that a Min is someone who says that Hashem isn't FIRST. That's it.
We also know the nusach of Yigdal:
קדמון לכל דבר אשר נברא ואין ראשית לראשיתו.
[See Yeshurun 22 p.798 and Da'as Emunah on the fourth ikkar]
Some Meforshim understand the Ibn Ezra on the first pasuk in the Torah to be saying that the world was sculpted from eternal matter.