2 Samuel 1:18

Also: having mentioned David's lamentation in general, before he comes to the particular description of it, he interposeth this verse by way of parenthesis; to signify, that David did not so give up himself to lamentation as to neglect his great business, the care of the commonwealth, which now lay upon him; but took particular care to fortify them against such further losses and calamities as he bewails in the following song; and by his example, and this counsel, to instruct the people, that they should not give up themselves to sorrow and despondency for their great and general loss; but should raise up their spirits, and betake themselves to action. He bade them: David being now actually king upon Saul's death, takes his power upon him, and gives forth his commands. The children of Judah: these he more particularly teacheth, because they were the chief, and now the royal tribe, and likely to be the great bulwark to all Israel against the Philistines, upon whose land they bordered; and withal, to be the most friendly and true to him, and to his interest. The use of the bow, i. e. the use of their arms, which are all synecdochically expressed under the name of the bow, which then was one of the chief weapons; and for the dexterous use whereof Jonathan is commended in the following song: which may be one reason why he now gives forth this order, that so they might strive to imitate Jonathan in the military skill, and to excel in it, as he did. It is written; not the following song, as many think, for that is written here, and therefore it was needless to refer us to another book for it; but this foregoing counsel and course which David took to repair the last loss, which is here mentioned but briefly, and in general terms; but, as it seems, more largely and particularly described in the book of Jasher; of which see on Joshua 10:13.