'Work' in the Bible

I am sure of this, that He who started a good work in you will carry it on to completion until the day of Christ Jesus.

Now if I live on in the flesh, this means fruitful work for me; and I don’t know which one I should choose.

So then, my dear friends, just as you have always obeyed, not only in my presence, but now even more in my absence, work out your own salvation with fear and trembling.

because he came close to death for the work of Christ, risking his life to make up what was lacking in your ministry to me.