An English born preacher (Edwin Fesche, now of Baltimore) taught this writer years ago that to be a valid ordinance of the Christian church, an observance had to be three things:
1. Instituted by Christ Himself
2. Practiced in the Acts of the Apostles
3. Explained in the Epistles of the N. T.
Only two ordinances meet these three criteria: Baptism and the Lords Supper.