Before considering the motivation that empowers Christian obedience positively, let us note some forms of motivation that are common but not helpful.
Sometimes we are motivated by guilt. We seek to do what God requires out of a sense of our failure and unworthiness before God. We strive to obey in order to remove the sense of God’s condemnation and judgment. We feel that if we can only live up to God's commands, we will escape the feeling of God’s displeasure. This sense of guilt can be a problem, even if we have an assurance of salvation.
Legalism is another problematic motivation. By legalism, I mean a system which prescribes a variety of rules that people are expected to obey, and which grants acceptance only to people who conform to the rules and expectations. In the New Testament, the Pharisees are the prime example of legalism, with their extensive rules about the Sabbath, tithing, washing, etc. Along with the rules there were strict codes of acceptance or rejection: those who kept the rules were accepted; those who failed to do so were unacceptable.
Unfortunately, legalism did not die out with the Pharisees. It is often found in Christian circles today. Sometimes it is expressed through arbitrary dress codes, strict rules governing church attendance, requirements that one adopt certain theological convictions. In some cases, the actual behaviour required by a legalistic system is desirable in and of itself, but the legalistic environment does not provide helpful motivations to do what is right. In a legalistic system, acceptance before God and man is always highly conditional.
12 we exhorted each one of you and encouraged you and charged you to walk in a manner worthy of God, who calls you into his own kingdom and glory.