ما سبب ضم الهاء في "عليهُ اللهَ" بسورة الفتح، وما تأثير ذلك على معنى الآية؟

Dhamm (ضم - vocalization with a "u" sound) of the letter Hā’ (هاء) in "alayhi Allah" (عليه الله) is the original pronunciation, because the origin of the Hā’ in the pronoun is "huwa" (هو). As for kasr (كسر - vocalization with an "i" sound) of the Hā’, it is incidental, caused by its proximity to the quiescent Yā’ (ياء ساكنة). Neither of the two recitations affects the meaning of the verse.