And this is his commandment - His commandment, by way of eminence; the leading, principal thing which he enjoins on us; the commandment which lies at the foundation of all true obedience.
That we should believe on the name of his Son Jesus Christ - See the notes at Mark 16:16. Compare John 16:1; Acts 16:31.
And love one another ... - This follows from the other, and hence they are mentioned as together constituting his commandment. Notes, John 13:35.