Luther: the first commandment

We ought to mark with what great diligence and ability Moses handles the first commandment, and explains it.  He was doubtless, an excellent doctor.  David afterwards was a gate or a door out of Moses.  For he had well studied in Moses, and so he became a fine poet and orator;  the Psalms are altogether syllogisms or concluding sentences out of the first commandment. Major, the first, is God's word itself; Minor, the second, faith.  The conclusion is the act, work and execution, so that it is done, as we believe.

When we believe the first commandment, and so please God, then all our actions are pleasing unto Him.

Tabletalk 270