[David O. McKay Office Journal]
at Presidency meeting: I called attention to a growing tendency in the Church to feel that no member of the Church should hold the sacrament while he himself partakes of it; further, that it is a breach of proper procedure to partake of it with the left hand. The Brethren felt we should keep away from formalities and leave it to the custom or development of the custom. They felt that while the partaking of the sacrament is a covenant and it is the custom to use the right hand in making covenants, failure to do so would not vitiate the covenant.
[McKay, David O., Office Journal]