Though I have bound (margin, chastened) and strengthened their arms, yet do they imagine mischief against me. The first clause of this verse is more accurately translated as follows: And yet I have instructed, have strengthened their arms.
Here we have another instance of God's goodness and Israel's ingratitude. He had done much for them, and would fain have done more; and yet the return they made was devising mischief against him. The arms are the seat and symbol of strength, as the hands and fingers symbolize skill; thus, in reference to the latter the psalmist says, "Blessed be the Lord my Strength, which teacheth my hands to war, and my fingers to fight;" and with regard to the former he says, "He teacheth my hands to war, so that a bow of steel is broken by mine arms."
Two benefits are here included in the prophet's enumeration. He instructed the arms, by which is meant that he showed them how and where to get strength. But this was not all; he not only directed to the source, and taught the secret of acquiring strength, he actually supplied strength, thereby giving them power to contend against and conquer their enemies.
At a time when "there was not any shut up, nor any left [that is, 'neither bond nor free'] nor helper for Israel … the Lord … saved them by the hand of Jeroboam the son of Joash."