When Does it Become Fardh to Learn a Mas-alah?

1. When something becomes fardh upon a person, it becomes fardh to learn the manner of doing it.
2. If something is mustahab then it is mustahab to learn the manner of doing it.
3. Since Namaaz (Salaat) is fardh, it is fardh to learn the masaail of Namaaz.
4. Similar is the case with fasting and other Shar’i injunctions.
5. When a person takes up employment or does business, etc. then it is incumbent to learn how to go about it according to the Shariah and act accordingly.
6. The above applies to actions which are fardh (or mustahab, etc.) upon everyone.

(Behshti Zewar)