“lazy.” See commentary on Prov. 6:6, “lazy one.”
“sense.” The Hebrew word is leb (#03820 לֵב), which is often translated “heart,” but this is one of those cases where that translation would cause confusion. In modern English, the word “heart” usually refers to emotion or passion, but that is not its meaning here. The function of the brain was unknown in biblical times, so things that we generally assign to the brain, like thinking, attitudes, understanding, and good sense, were assigned to the heart. In this context, leb, “heart” refers to the activity of the mind that includes good sense.
A lazy person lacks good sense, because he does not do those things that would sustain his life, allow him to be in a position to help others, and build up rewards in the next life. The Bible says we are to work so that we can give to others (Eph. 4:28), not just do what we have to in life so we “just get by.” Even when God put Adam and Eve in the Garden of Eden they were to work it and “keep” it (or, watch over it; guard it. Gen. 2:15). God created people to do good works (Eph. 2:10), and that is a sacred duty. [For more on the Hebrew word leb and “heart,” see commentary on Prov. 15:21, “sense”].