Charles H. Spurgeon on Psalms 18:21

Here the assertion of purity is repeated, both in a positive and a negative form. There is "I have" and "I have not," both of which must be blended in a truly sanctified life; constraining and restraining grace must each take its share. The words of this verse refer to the saint as a traveler carefully keeping to "the ways of the Lord," and "not wickedly," that is, designedly, wilfully, persistently, defiantly forsaking the ordained pathway in which God favours the pilgrim with his presence. Observe how it is implied in the expression, "and have not wickedly departed from my God," that David lived habitually in communion with God, and knew him to be his own God, whom he might speak of as "my God." God never departs from his people, let them take heed of departing from him.