if RasulAllah sallallahu `alayhi wa sallam did not leave out an action - even once - it is proof for its being wajib. [fat'H al-Qadir, bab al-adhan] suppose an action that was done always, and not left out even once; if the SaHabah did not object to those who omitted such an action it is proof that such an action is sunnah; or else [if they objected] it is proof of the action being wajib. [fat'H al-Qadir, bab al-i`ytikaf] - action done by RasulAllah sallallahu `alayhi wasallam. - maqrunatun is used as an emphasis on the conjuction, that is: doing the action always AND not omitting it even once. such that both attributes are together.