My soul thirsts for God, for the living God; When shall I come and appear before God? Psalms 42:2 NASB https://bible.com/bible/100/psa.42.2.NASB

Comment from John Macarthur Study Bible:

† 4: 10 living water. The OT is the background for this term, which has important metaphorical significance. In Jer 2: 13 , Yahweh decries the disobedient Jews for rejecting Him, the “fountain of living waters.” The OT prophets looked forward to a time when “living waters will flow out of Jerusalem” ( Eze 47: 9 ; Zec 14: 8 ). The OT metaphor spoke of the knowledge of God and His grace which provides cleansing, spiritual life, and the transforming power of the Holy Spirit (cf. Is 1: 16– 18 ; 12: 3 ; 44: 3 ; Eze 36: 25– 27 ). John applies these themes to Jesus Christ as the living water which is symbolic of eternal life mediated by the Holy Spirit