This sentence could be boiled down to this: Qui habitat commorabitur. He who dwells, shall linger. Qui is a relative pronoun (masculine, singular, nominative), and is the subject of commorabitur. It begins “He who,” or simply “Who.”

Commoror, commorari is a deponent verb meaning to linger, to stay. Deponent verbs are passive in form but active in meaning, so the translation is not “he will be lingered” (which would not make sense) but “he will linger” (3rd person singular, future tense). If you remove the ‘ur’ at the end you can see what the active form would have looked like: commorabit. But deponents use a passive form.

Umbra,ae = shadow, shade. We recall the phrase Alis suis obumbrabit tibi. Obumbrare clearly has umbra as its root. The umbrella, which not only shields us from rain but also provides shade on a sunny day, has its etymological origin here.

Altissimi: A superlative. Altus=high. Altior=higher. Altissimus=the highest, or the Most High, which is here a proper name for God. The ending, ‘i’, makes it genitive, so ‘of the Most High.’