I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting [aiōnios, ‘eternal’] life” (John 4:13-4).
“Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink. He that believeth [pisteuō, ‘have faith’] on me, as the scripture hath said, out of his belly shall flow rivers of living water” (John 7:37-8).
“But unto him that keepeth my commandments I will give the mysteries of my kingdom, and the same shall be in him a well of living water, springing up unto everlasting life” (D&C 63:23).
“Then knowledge through our Lord and Savior Jesus Christ is the grand key that unlocks the glories and mysteries of the kingdom of heaven” (Joseph Smith, HC 5:388).
The living water is more than just the sacramental cup given to a person by a priesthood holder.
It is Christ alone who symbolically gives a person the living water that causes him or her to never thirst spiritually in mortality, and springs up to eternal life.