Manārah is a prominent place for a light, mumsā evokes evening or the state of spending the evening, and rāhib means monk. Mutabattil is an active participle from Form V, suggesting withdrawal from ordinary pursuits for devotion.
Manārat mumsā rāhib forms a connected construct sequence. Its role is not to identify a particular monk's biography but to establish the recognizable image of a lamp plainly visible in the dark.
The simile draws on a cultural setting in which a light in a religious retreat could serve as a distant point of brightness. The text's direct claim is a comparison of radiance; the surrounding cultural association helps explain why that image is powerful.