Here Nahum enters on his special subject, for which the previous verses have prepared the way, namely, to assure his people of safety in Jehovah under the impending attack of Sennacherib (Nah 1:7), and to announce the doom of Nineveh, the capital of the Assyrian foe (Nah 1:8). The contrast of Nah 1:7, Nah 1:8 heightens the force.
he knoweth - recognizes as His own (Hos 13:5; Amo 3:2); and so, cares for and guards (Psa 1:6; 2Ti 2:19).