Believe me ... - Believe my declarations that I am in the Father, etc. There were two grounds on which they might believe; one was his own testimony, the other was his works.
Or else - If credit is not given to my words, let there be to my miracles.
For the very works’ sake - On account of the works; or, be convinced by the miracles themselves. Either his own testimony was sufficient to convince them, or the many miracles which he had performed in healing the sick, raising the dead, etc.