A.T. Robertson Commentary John 4:14

"but whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall become in him a well of water springing up unto eternal life." — John 4:14 (ASV)

That I shall give him (ου εγω δωσω αυτω). Relative ου attracted to the case (genitive) of the antecedent (υδατος). Future active indicative of διδωμ.

Shall never thirst (ου μη διψησε εις τον αιονα). The double negative ου μη is used with either the future indicative as here or the aorist subjunctive, the strongest possible negative. See both constructions (ου μη πειναση and ου με διψησε) in Joh 6:35. Jesus has not answered the woman's question save by the necessary implication here that he is superior to Jacob.

A well of water springing up unto eternal life (πηγη υδατος αλλομενου εις ζωην αιωνιον). "Spring (or fountain) of water leaping (bubbling up) unto life eternal." Present middle participle of αλλομα, old verb, in N.T. only here and Ac 3:8; 14:10. The woman's curiosity is keenly excited about this new kind of water.