What is meant by the doors of Ijtihaad are closed?

Answer

The Doors of Ijtihaad being closed applies to the Usool (Principles) and Furoo' (particular/ detailed masaa-il) formulated by the Aimmah Mujtahideen. The issues which the Aimmah Mujtahideen had settled and finalized may not be subjected to ijtihaad. For example, the Aimmah Mujtahideen of all Math-habs have unanimously ruled that three Talaaqs uttered in one breath are three, not one as the deviant Salafis opine on the basis of their understanding of certain Hadith narrations.

The Doors of Ijtihaad having closed is not applicable to new developments, e.g. preforming Salaat on the moon or using scientific instruments/ calculations to determine the Islamic months or to decide the permissibility or impermissibility of performing Salaat in the air or for deciding the impermissibility of digital picture, etc., etc.

The rulings for all new developments will be based on the Principles evolved by the Aimmah Muhtahideen and also on similar particular mas'alahs already existing in the Shariah. Re-interpreting existing Principles and Particulars is haraam.