When the subject is already known and its repetition adds nothing needed, stating it again may burden an utterance. This consideration is called avoiding pointless redundancy (الاحتراز عن العبث). ‘Pointless’ here refers to the rhetorical purpose of a particular situation, not necessarily to an intrinsically meaningless or sinful utterance.
للاحتراز عن العبث بناء على الظاهر
To avoid apparently unnecessary repetition.
Example:
Question: «مَنْ حَضَرَ؟» — Who came?
Answer: «زَيْدٌ» — Zayd.
A fuller reply, «زَيْدٌ حَضَرَ», is possible, but the question already supplies the predicate. If emphasis or clarification is needed, however, the fuller form may be preferable. Thus rhetorical value—not simply word count—governs omission.