"The Oath", taken at the initiation rites into a new Covenant.
From Ars Magica 3rd Edition rulebook. This is Grimgroth's example
oath to Mistridge.

I, Grimgroth of House Jerbiton, do humbly ask for acceptance into the 
Covenant of Mistridge. I do so of my own will, under no influences other
other than my own; no magicks or powers mundane force me here today.
I understand that my life is forfeit should this or any other part of
my oath be found false. Here I stand, with full knowledge of what I do.

I swear by the Order, my life, and all I hold dear, that I am Grimgroth
follower of Jerbiton, filius of Vlaria, fully trained solely in the ways
of Hermetic Magic and none other. I here truthfully state I have never 
consorted with or aided demons, diabolists, or practitioners of magic
other than those sanctioned by the Order, and will continue this practice
as long as I live.

I further swear the title of Magus is properly mine, being conferred upon
me by Nostrorum in the year 1067, at the Covenant Duresca, within the
Iberian tribunal, I, Grimgroth, do now renounce all ties, oaths, and
loyalties, binding or otherwise, to my parens and the Covenant of my
apprenticeship.

Now I begin anew, and give myself wholly to Mistridge. I understand all
that this entails, and agree to all terms within the Covenant charter
for now and for all time. In addition, I swear to follow both the Code
of Hermes and the Peripheral Code, lest I lose my title of Magus, position
within my House, and place within this Covenant.

From this day forward, Mistridge shall be my home. I agree to make 
Mistridge's goals mine own, its allies mine own, its enemies mine own,
its riches mine own, and its hardships mine own. I swear never, by action
or inaction, to allow the Covenant to come to harm, in the physical, 
magical, spiritual, or personal sense. I agree never to represent
Mistridge to others, sign binding pacts, or make oaths regarding its
members or its welfare without first being so empowered by the Covenant.
In all respects I will uphold the reputation  and honor of this, my
new home, and consider its welfare above my own.

This is my solemn covenant. Mistridge's very life is now mine own.