a spring of water welling up to eternal life

See John 4:13-14.

    ¹³Jesus answered, "Everyone who drinks this water will be thirsty again, ¹⁴but whoever drinks the water I give him will never thirst. Indeed, the water I give him will become in him a spring of water welling up to eternal life."

Let us think about what ‘thirsty again’ means.

Our physical body is mortal. Our body has physiological needs. So, we drink physical water and eat physical food.  We have to repeat this. We value physical things and do not know they can’t satisfy our soul. This misunderstanding can put us in pursuit or competition for the limited resources. This pursuit or competition can make us tired of the repetition. ‘thirsty again’ expresses this. But if we drink the water Jesus gives will never thirst, giving eternal satisfaction and eternal life. It will become a spring of water welling up forever.

This water satisfies our soul and does not require repetition

People who depend only on physical water will be continuously thirsty. Either ignorant or resentful of their God-implanted need for spiritual water, they will always look in the wrong direction for satisfaction. Jeremiah had proclaimed this truth centuries earlier: “My people have committed two sins: They have forsaken me, the spring of living water, and have dug their own cisterns, broken cisterns that cannot hold water” (Jeremiah 2:13). [2]

God Himself is the spring of living water (Jeremiah 2:13). The sacrifice of Jesus on the cross qualified us (His believers) to retain inside us this spring of water welling up to eternal life.

References

[1] The Holy Bible: New International Version (Anglicised Edition, 2011). (2011). (Revised and updated edition, Jn 4:13-14). London: Hodder & Stoughton.

[2] Gangel, K. O. (2000). John (Vol. 4, p. 76). Nashville, TN: Broadman & Holman Publishers.