To follow Jesus, we must listen, and keep listening, to the words of Christ. The 1st century Christians were not just believers, but active learners. Jesus gives eternal life, which starts in the present (as denoted in the present tense “has”) and continues into the future.
“Truly, truly, I say to you, he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life.