What does Psalm 36:9 mean?

David has praised God for His mercy and gifts to mankind (Psalm 36:5–8). The greatest of these blessings is the offer of salvation. So, here, David praises the Lord for His "fountain of life" and being the Giver of light. Fountains and other images of moving water are used in the Bible with connection to life (Zechariah 14:8; Revelation 22:1; John 4:13–14). Light is the biblical ideal of truth, goodness, and knowledge.

The gospel of John reveals clearly that Jesus came into the world to give life and light to those who believe on Him (John 1:3; 14:6). In John 10:10 Jesus contrasts the thief who steals sheep with Himself. He states: "The thief comes only to steal and kill and destroy. I came that they may have life and have it abundantly." Before He raised Lazarus from the dead, Jesus told Lazarus' sister Martha, "I am the resurrection and the life. Whoever believes in me, though he die, yet shall he live, and everyone who lives and believes in me shall never die" (John 11:25–26). He told the scribes and Pharisees: "I am the light of the world. Whoever follows me will not walk in darkness, but will have the light of life" (John 8:12).

Believers in Jesus do not walk through life blindly. They follow Jesus, who guides them as surely as the pillar of fire guided Israel by night (Exodus 13:21–22).