Jamieson, Fausset and Brown on James 4:8

8. Draw nigh to God--So "cleave unto Him," De 30:20, namely, by prayerfully (Jas 4:2, 3) "resisting Satan," who would oppose our access to God.

he will draw nigh--propitious.

Cleanse ... hands--the outward instruments of action. None but the clean-handed can ascend into the hill of the Lord (justified through Christ, who alone was perfectly so, and as such "ascended" thither).

purify ... hearts--literally "make chaste" of your spiritual adultery (Jas 4:4, that is, worldliness) "your hearts": the inward source of all impurity.

double-minded--divided between God and the world. The "double-minded" is at fault in heart; the sinner in his hands likewise.