Say (O Muhammad SAW): "If the Most Beneficent (Allah) had a son (or children as you pretend), then I am the first of Allah's worshippers [who deny and refute this claim of yours (and the first to believe in Allah Alone and testify that He has no children)]." [Tafsir At-Tabari].
Sema: Ingeli kuwa Rahmani ana mwana, basi mimi ningeli kuwa wa kwanza kumuabudu.