Tertullian

“ Shall human volition have more licence than Divine power? I am mindful that I am free from the world, [1] not from God. Thus it is my part to perform, without external suggestion thereto, an act of respect to my Lord, it is His to enjoin. I ought not merely to pay a willing obedience to Him, but withal to court Him; for the former I render to His command, the latter to my own choice.
But it is enough for me that it is a customary practice for the bishops withal to issue mandates for fasts to the universal commonalty of the Church ”

“ You lay down a prescription that this faith has its solemnities “appointed” by the Scriptures or the tradition of the ancestors; and that no further addition in the way of observance must be added, on account of the unlawfulness of innovation. Stand on that ground, if you can. ”