Deep calls unto deep at the noise of your waterfalls: all your waves and your billows are gone over me.
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Augustine of Hippo
AD 430
12. "Deep calleth unto deep with the voice of thy water-spouts" (ver. 7). I may perhaps finish the Psalm, aided as I am by your attention, whose fervour I perceive. As for your fatigue in hearing, I am not greatly solicitous, since you see me also, who speak, toiling in the heat of these exertions. Assuredly it is from your seeing me labouring, that you labour with me: for I am labouring not for myself, but for you. "Deep calleth unto deep with the voice of thy water-spouts." It was God whom he addressed, who "remembered him from the land of Jordan and Hermon." It was in wonder and admiration he spake this: "Abyss calleth unto abyss with the voice of Thy water-spouts." What abyss is this that calls, and to what other abyss? Justly, because the "understanding" spoken of is an "abyss." For an "abyss" is a depth that cannot be reached or comprehended; and it is principally applied to a great body of water. For there is a "depth," a "profound," the bottom of which cannot be reached by soun...
Flood-gates. The Hebrews imagined there were immense reservoirs of water above, (Calmet) which might serve to drown the earth, as at the deluge, Genesis vii. 11. Both heaven and earth seemed to be armed against the psalmist. (Haydock)
One affliction succeeded another, (Calmet) and God appeared to have abandoned his servants to temptations. But he enables them to come off with victory, and fills them with more joy in their trials: so that they may sing in heart, and pray. (Worthington)