ونهي عن التصرفات الشرعية: كالنهي عن الصوم في يوم النحر، والصلاة في الأوقات المكروهة، وبيع الدرهم بالدرهمين
The second category includes fasting on the day of sacrifice, prayer in disapproved periods, and a usurious exchange of two dirhams for one.
Fasting and prayer are recognized acts of worship, and sale is a legally constituted transfer. Yet the specific time, condition, or accompanying element makes these examples prohibited.
It must therefore be determined whether the prohibition concerns the act as such or an external condition or attached characteristic of that act.