«والأصل الذي لا يعدل عنه ما لم تمس حاجة إلى زيادة الارتباط هو الضمير»
The primary link, not abandoned without need for additional connection, is the pronoun.
A pronoun provides a specific antecedent within the second clause. It identifies whose condition is being described. Wāw can add an explicit clause-level link, but it is not merely a mandatory substitute for every pronoun, nor does a pronoun necessarily have to be expressed in a separate word.