Obedience

"There are only two ways of salvation: by the law or by grace. If salvation is to happen by the law, perfect obedience is necessary. There can be no blemishes or shortcomings, for the law will never show mercy. It knows nothing of grace or forgiveness. It demands perfection, because whoever transgresses in one tiny detail transgresses the whole of God’s law: “For whoever keeps the whole law but fails in one point has become accountable for all of it” (James 2:10). Getting to heaven through obedience to the law requires perfection. Merely doing your best will prove insufficient; good intentions are not enough. It is vitally important to grasp exactly how much the law demands if we think we are going to be in a right relationship with God through law-keeping. Simply put, “By works of the law no one will be justified” (Gal. 2:16).
- Derek Thomas

"Sinners cannot obey the gospel, any more than the law, without renewal of heart."
- J.I. Packer

Contrasting Legalism and Obedience: Legalism is a person's attempt to ATTAIN or MAINTAIN salvation through his or her own works, merit, humility, sound judgement or good character. Obedience, on the other hand, is the fruit of the work of Christ in which the Holy Spirit renews the heart to which it responds to its salvation by a willing and glad obedience. A quickened heart WANTS to obey ... not in order to be saved but because it is saved.

Scriptural commands (or imperatives) do not declare our ability, but our duty; what we ought to do. However, the power to obey them comes ONLY from the One that gave the command - the Spirit uniting us to Christ.