The original Latin Rule of Order was penned with the assistance of the young Cistercian Abbott, Bernard of Clairvaux. The rule is very similar to the modified Benedictine rule used by the Cistercian order. This makes perfect sense as the two orders were closely related and linked.
The Primitive Rule of the Templars
Here Begins the Rule of the Poor Knighthood of the Temple
9. You who renounce your own wills, and you others serving the sovereign king with horses and arms, for the salvation of your souls, for a fixed term, strive everywhere with pure desire to hear matins and the entire service according to canonical law and the customs of the regular masters of the Holy City of Jerusalem. 0 you venerable brothers, similarly God is with you, if you promise to despise the deceitful world in perpetual love of God, and scorn the temptations of your body: sustained by the food of God and watered and instructed in the commandments of Our Lord, at the end of the divine office, none should fear to go into battle if he henceforth wears the tonsure.
10. But if any brother is sent through the work of the house and of Christianity in the East--something we believe will happen often--and cannot hear the divine office, he should say instead of matins thirteen paternosters; seven for each hour and nine for vespers. And together we all order him to do so. But those who are sent for such a reason and cannot come at the hours set to hear the divine office, if possible the set hours should not be omitted, in order to render to God his due.
The Manner in which Brothers should be Received
11. If any secular knight, or any other man, wishes to leave the mass of perdition and abandon that secular life and choose your communal life, do not consent to receive him immediately, for thus said my lord St Paul: Probate spiritus si ex Deo sunt. That is to say: 'Test the soul to see if it comes from God.' Rather, if the company of the brothers is to be granted to him, let the Rule be read to him, and if he wishes to studiously obey the commandments of the Rule, and if it pleases the Master and the brothers to receive him, let him reveal his wish and desire before all the brothers assembled in chapter and let him make his request with a pure heart.
Image: Castle Eltz ~ built in 1148 AD
Music: ‘The Most Beautiful Templar Chant Ever Sung’ ~ Vox Medieval (AI, but a good song)
youtube.com/watch?v=j9JzlgPeUrc