1 Peter 2:15-16

For God wants you to silence the ignorance of foolish people by doing good.  Live as free people, not using your freedom as a pretext for evil, but as God’s slaves.

Our doing good doesn't qualify us as candidates for salvation. When we place too much importance on our doing good it can lead us down a path of sin. We are saved by grace through faith in Christ Jesus alone. That being said, that grace empowers us to live differently, as a response to His love for us displayed at the cross. Living in the freedom of that grace produces the good that we ought to do in love. That freedom in Christ does not give us the right to presume upon the cross and do good for selfish gain. We must always carefully consider our motives for doing good.