In the following passage,
Quia oratio illa iam fortis est, quae fit in spiritu humili et corde contrito; qui autem deliciis fruitur, spiritum humilem et cor contritum habere non potest; manifestum est quoniam oratio sine ieiunio gracilis est et infirma: et ideo quicumque pro aliqua necessitate voluerunt orare, ieiunium adiutorium est orationis.
Is that “manifestum est quoniam oratio sine ieiunio gracilis est et infirma“ a parenthesis? It does not seem to have any relation to any other clause in this sentence. Also: what is that “ieiunium adiutorium est orationis“ doing? It also does not seem to relate to any other clause, and “et ideo quicumque pro aliqua necessitate voluerunt orare“ has no meaning alone (And because of that everyone who prayed for some need…). “Adiutorium est“ made me remember a deponent verb, but I did not find the verb “adiutorior“ or something like that, so unless it is an extremely rare word (or the form I supposed to be the present is not actually it), I think it is not the case.
Here is the text, if you want to take a closer look: Thomas de Aquino, Catena aurea in Matthaeum, cap. 5-9