Adam Clarke on Proverbs 31:18

She perceiveth that her merchandise is good -

8. She takes care to manufacture the best articles of the kind, and to lay on a reasonable price that she may secure a ready sale. Her goods are in high repute, and she knows she can sell as much as she can make. And she finds that while she pleases her customers, she increases her own profits.

9. She is watchful and careful. Her candle - her lamp, burns all night, which is of great advantage in case of sudden alarms; and in the times and places where there were so many banditti, this was a very necessary family regulation. Perhaps some works were carried on during the night, those employed sleeping in the daytime. Thus labor never stood still; whilst some slept, others worked. This was no unusual thing in ancient times; and it prevails now; but alas! little children are often thus employed to help to support their indigent parents, and to fill the coffers of their unfeeling taskmasters.