Learning NT Greek is a valuable tool that helps a believer understand better what God has said to him. John 4:14 provides a good example of that value:
Joh 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 be in him a well of water springing up into everlasting life.
Joh 4:14 ὃς δ᾽ ἂν πίῃ ἐκ τοῦ ὕδατος οὗ ἐγὼ δώσω αὐτῷ, οὐ μὴ διψήσῃ εἰς τὸν αἰῶνα· ἀλλὰ τὸ ὕδωρ ὃ δώσω αὐτῷ γενήσεται ἐν αὐτῷ πηγὴ ὕδατος ἁλλομένου εἰς ζωὴν αἰώνιον.
But whoever should drink from the water that I (emphatic) will give him will by no means thirst forever [or you could say, ever]; but the water that I will give him will be in him a well of water springing up to eternal life [my literal translation].
Whereas the English text has the promise that Jesus sets before the Samaritan woman as whoever drinks of the water that He will give him “shall never thirst,” the Greek text is stronger because it has both emphatic negation (οὐ μὴ διψήσῃ [“shall never thirst” or “will by no means thirst”]) and three words that the English does not translate: εἰς τὸν αἰῶνα.
These three words are a Greek idiom that means “forever.” Jesus’ promise to the woman of the water that He would give her was such that whoever would drink of it would by no means thirst forever! 
Also, the Greek text has an emphatic pronoun (ἐγὼ) that emphasizes Him as the Giver of this water. Jesus was thus using an emphatic pronoun, emphatic negation, and a Greek idiom to declare that a person who would drink the water that He gives would by no means ever thirst after he drinks of that water!
 Cf. the NET Bible note for this part of the verse: “NET Notes (Joh 4:14) 35 tn Grk “will never be thirsty forever.” The possibility of a later thirst is emphatically denied.”
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