أريد تعليل كتابة الألف اللينة على صورتها في كلمتي العلا يحتذى

The reasoning behind writing the soft Alif in the words “al-a” is explained. The word “al-a” is written with a stretched Alif because the verb is trilateral (al-a) and in the present tense the Alif and Waw are added (yulaw). Therefore, the stretched Alif must be written in this way (al-a). As for the word “yuhatha”, because the verb has more than three letters, the soft Alif must be written as Kasra and because it is not preceded by a Ya.