John Trapp on Isaiah 30:7

Ver. 7. For the Egyptians ſhall help in vain and to no purpoſe] Heb. in vanity and inanity; ſuch are creature-comforts if relyed on: a very magnum nihil.

Therefore have I cryed] but could not get audience.

Their ſtrength is to ſit ſtill] to bide at home, and behold the ſalvation of the Lord; for the Prophet here ſeemeth to relate to that, Exod. 14.14. Contented godlineſs is great gain ſaith the Apoſtle, 1 Tim. 6.6. and quiet godlineſs is great ſtrength, ſaith the Prophet here; Their ſtrength is to fit ſtill: as good ſit ſtill (ſaith our Engliſh proverb) as riſe and fall. The word here rendred ſtrength, is Rahab, which ſignifieth pride and power, and is ſometimes put for Egypt her ſelf, Pſal. 86. Hence the Vulgar tranſlation here is, Superbia tantum eſt, quieſce; Egypt is but a flask or a piece of proud fleſh: ſhe is all in oſtentation, but will not anſwer thine expectation: therefore keep home, and be quiet. Others rendring the Text as we do, ſet this ſenſe upon it; your Rahab or Egypt is to ſit ſtill, and to hold you content: by ſo doing you ſhall have an Egypt: whatſoever ſuccour you might think to have that way, you ſhall have it (and better) this way, ſi tranquillo & ſedato ſitis animo, if you can compoſe your ſelves and get a Sabbath of ſpirit.