﴿ ٱلَّذِينَ ءَامَنُوا۟ بِـَٔايَٰتِنَا وَكَانُوا۟ مُسْلِمِينَ ﴾

“[O you] who have attained to faith in Our messages and have surrendered your own selves unto Us!”

those who believed alladhīna āmanū adjectivally qualifies ‘ibādī ‘My servants’ in Our signs — the Qur’ān — and had submitted themselves to Me.