Blessed is the man who walks not in the counsel of the wicked, nor stands in the way of sinners,  nor sits in the seat of scoffers; but his delight is in the law of the LORD, and on his law he meditates day and night.  Psalm 1:1-2

When men are living in sin they go from bad to worse. At first they merely walk in the counsel of the careless and ungodly, who forget God—the evil is rather practical than habitual—but after that, they become habituated to evil, and they stand in the way of open sinners who willfully violate God's commandments; and if let alone, they go one step further, and become themselves pestilent teachers and tempters of others, and thus they sit in the seat of the scornful.

They have taken their degree in vice, and as true Doctors of Damnation they are installed, and are looked up to by others as Masters in Belial. But the blessed man, the man to whom all the blessings of God belong, can hold no communion with such characters as these. He keeps himself pure from these lepers; he puts away evil things from him as garments spotted by the flesh; he comes out from among the wicked, and goes without the camp, bearing the reproach of Christ. O for grace to be thus separate from sinners. 

"His delight is in the law of the Lord." He is not under the law as a curse and condemnation, but he is in it, and he delights to be in it as his rule of life; he delights, moreover, to meditate in it, to read it by day, and think upon it by night. He takes a text and carries it with him all day long; and in the night-watches, when sleep forsakes his eyelids; he museth upon the Word of God. In the day of his prosperity he sings psalms out of the Word of God, and in the night of his affliction he comforts himself with promises out of the same book. "The law of the Lord" is the daily bread of the true believer.

Spurgeon, Charles.  The Treasury of David.  Volume 1.  McLean, Virginia:  MacDonald Publishing Company.  pp. 1-2.