John 6:28, "Then said they unto him, What shall we do, that we might work the works of God?"
All throughout history, mankind has been seeking ways to do the works of God. Everyone has a knowledge within them of the reality of God (Rom. 1:18-20), and a desire to be right with Him. However, just as with these Jews, few agree with the Lord as to how to do it. These Jews were willing to do something to obtain salvation, but they were not willing to commit themselves to Jesus and accept His gift.
This is one of the major differences between Christianity and the religions of the world. Religion is willing to make sacrifices to obtain right standing with God, but Christianity recognizes our complete inability to ever do enough to save ourselves and calls for total faith and reliance on what Jesus did for us.
No one deserves salvation. It cannot be earned by what the Bible calls "dead works" (Heb. 6:1; 9:14). Dead works include all religious activities, good deeds, or charity that one may do as a means of being justified before God.
Faith towards God and what He has done through Christ Jesus is the only means of receiving His free gift of salvation. He only asks us to believe.