This notes either,
1. The strength of which they boasted. See Psalms 44:6, Psalms 46:9. Or,
2. Their malicious or mischievous designs. See Psalms 7:12, Psalms 11:2 37:14. Or,
3. Their virulent tongues, which are compared to bows that shoot their arrows, even bitter words; as it is said Psalms 64:3: compare Jeremiah 9:3. Or,
4. Their procreating virtue, which may well be compared to a bow, both because it is called a man's strength, Genesis 49:3, and because children, which are the effects of it, and are as it were shot from that bow, are compared to arrows, Psalms 127:4,5. And this seems best to agree with the following verse. They that stumbled; or, were weak, or feeble, in body and spirit, that had no strength to conceive, which was once Sarah's case, Hebrews 11:11; or to bring forth, which was Israel's condition under Hezekiah, 2 Kings 19:3. Are girt with strength; are enabled both to conceive and to bring forth, as the church was, Isaiah 66:9.