Albert Barnes on Matthew 22:38

This is the first and great commandment. This commandment is found in De 6:5. It is the first and greatest of all; first, not in order of time, but of importance; greatest in dignity, in excellence, in extent, and duration. It is the fountain of all others. All beings are to be loved according to their excellence. As God is the most excellent and glorious of all beings, he is to be loved supremely. If He is loved aright, then our affections will be directed towards all created objects in a right manner.