Now see the rule in the source's legal example.
وَالْمُطَلَّقَاتُ يَتَرَبَّصْنَ بِأَنْفُسِهِنَّ ثَلَاثَةَ قُرُوءٍ
Meaning for this lesson: divorced women wait for 3 quru'1; this is their prescribed waiting period2.
Notice two separate pieces of wording:
• ثَلَاثَةَ — the number 3 is Khas and fixes the count.
• قُرُوءٍ — the source discusses more than one established meaning for this word.
The fixed number and the possible meaning of the other word must not be mixed together.
1. Quru': in this source discussion, a word used for menstrual periods and periods of purity; evidence is needed to select the intended meaning.
2. Waiting period ('iddah): the prescribed period after divorce discussed in this source example; its detailed rulings are not taught here.