Yaga' (יָגַע) means to toil, labor strenuously, or become weary from exertion. It appears about 26 times in the Old Testament and conveys both physical exhaustion and the labor that leads to it. The noun yagea' refers to the product of hard work. Isaiah 40:28 famously declares that God does not grow weary (yaga'), contrasting divine endurance with human frailty.
The theological use of yaga' highlights the contrast between human limitation and divine strength. Isaiah 40:28–31 is the centerpiece: God never wearies, and He gives strength to those who wait on Him. The term also carries covenantal weight — in Haggai 1:11, God withholds the fruit of toil because the people neglected His house. Jeremiah 51:58 warns that nations who toil for vanity will grow weary in vain. True fruitful labor only comes as a gift from God (Psalm 127:1–2).