Jesus answered, “The work of God is this: to believe in the one he has sent.”
Jesus has just told (v27) the crowds that working to sustain Eternal Life was more important than working to sustain this present, worldly life. The crowds asked the intelligent question, given that they had the Mosaic law with all its requirements: What are the works God requires? They might have been expecting Jesus to answer “all of them,” or perhaps single out a few of the Ten Commandments. Instead, he rather shockingly tells them to believe in himself.
Shocking…. because he told them that Eternal Life, Life with God, was more important than the life of/in the world. And because he told them that it wasn’t about the law, which had been the focus of their spiritual lives. Rather, he told them that it was about him, about believing in him.
“Believe…” The Greek word often used in this context meant to trust, to rely upon. So his message in verse 29 was that if you want Eternal Life, Life-with-God, you must rely upon Jesus.
He drove the point home a few moments later in verse 40: “For my Father’s will is that everyone who looks to the Son and believes in him shall have eternal life, and I will raise them up at the last day.”
Shocking, yes, but clear enough…..