Charles H. Spurgeon on Psalms 58:2

In heart ye work wickedness, etc. The psalmist doth not say, they had wickedness in their heart, but that they did work it there: the heart is a shop within, an underground shop; there they did closely contrive, forge, and hammer out their wicked purposes, and fit them into actions; yea, they weighed the violence of their hands in the earth. That's an allusion to merchants, who buy and sell by weight; they weigh their commodity to an ounce; they do not give it out in gross, but by exact weight. This saith the psalmist, they weigh the violence of their hands; they do not oppress grossly, but with a kind of exactness and skill, they sit down and consider what and how much violence they may use in such a case, or how much such a person may endure, or such a season may bear. They are wiser than to do all at once, or all to one, lest they spoil all. They weigh what they do, though what they do be so bad that it will hold no weight when God comes to weigh it. Nor do they arrive at this skill presently, but after they have, as it were, served an apprenticeship at it; and they bind themselves to the trade very early; for as it follows at the third verse of the Psalm, The wicked are estranged from the womb: they go astray as soon as they be born, speaking lies, that is, they are estranged both by nature and by early practice; they lose no time, they go to it young, even "as soon as they are born, "as soon as they are fit for any use, or to do any thing, they are using and setting themselves to do wickedly. Joseph Caryl.