أَلَا لَا تَصُومُوا فِي هَذِهِ الْأَيَّامِ
Do not fast on these days.
The expression prohibits fasting on the specified days. Yet if someone makes a vow to fast on such a day, the wording alone does not settle every question about the vow's legal formation, performance, or consequences.
The analysis separates the underlying character of fasting as worship from the disapproved time attached to it. Hanafi and Shafiʿi reasoning may lead to different conclusions; one cannot insert every detailed conclusion into the prohibition itself.