What is the ruling on shortening hair to less than the length of a fingertip according to the Four Imams: obligatory or recommended?

It is sufficient for a pilgrim (Hajj or Umrah) to shorten their hair by less than the length of a fingertip (anmula), but the shortening must be from all parts of the head. There is no minimum limit for what is sufficient as shortening; even the smallest part is sufficient because it is called "taqseer" (shortening). Shortening or shaving is obligatory for all hair for both men and women. Shaving is preferable to shortening for men.