Avoiding the word 'ought'

Thanks to Tim Challies for these words written 480 years ago which encouraged me today:

'Here I must take counsel of the Gospel, I must hearken to the Gospel, which teacheth me, not what I ought to do (for that is the proper office of the Law), but what Jesus Christ the Son of God hath done for me: to wit, that he suffered and died to deliver me from sin and death. The Gospel willeth me to receive this, and to believe it. And this is the truth of the Gospel. It is also the principal article of all Christian doctrine, wherein the knowledge of all godliness consisteth. Most necessary it is therefore, that we should know this article well, teach it unto others, and beat it into their heads continually.'

(Martin Luther on St. Paul’s Epistle to the Galatians)