Proverbs 6:6 says, “Go to the ant, you sluggard; consider its ways and be wise!” Paul says, when serving, to serve as if we are serving the Lord himself (Colossians 3:23-24). Christian apologist Cliffe Knechtle says that laziness is a sin because “laziness is essentially saying, ‘God, you have given me nothing of significance and importance. Therefore, I can fritter my life away being lazy, not developing my physical talents, or my intellectual talents, or my my spiritual talents because guess what? It really doesn’t matter.'”
Proverbs has lots to say about laziness. For example, it says that “whoever is slack in his work is a brother to him who destroys” (Proverbs 18:9. Proverbs 26:13 says that lazy people make up excuses: “The sluggard says, ‘There is a lion in the road! There is a lion in the streets!'” They refuse to work: “The desire of the sluggard kills him, for his hands refuse to labor” (21:25). And they are wise in their own eyes: “The sluggard is wiser in his own eyes than seven men who can answer sensibly” (26:16).
Finally, we know that laziness leads to poverty, but “whoever gathers little by little will increase it (wealth)” (13:11). So Cliffe is exactly right–laziness is a sin. It’s a sin because we take the talents God has given us and we refuse to put them to use. When we put the talents to use, we increase little-by-little, piece-by-piece, and we are able to help many, many people in need.