I agree we all "know" this, but did the Old Testament folks know this? Before Jesus came, how could they "leave everything and follow Him", if that is the only way to eternal life? Did not the law inform them over and over that commandment keeping was required to have a relationship with God? Was not commandment keeping an evidence of their belief in God? I realize it can also be a sign of trust in self.Some say that Jesus wouldn’t do that. He would never use a false belief to illustrate a truth. Wouldn’t He? I remembered His encounter with the rich young man:
Matt 19:16 And behold, one came up to him, saying, "Teacher, what good deed must I do, to have eternal life?"
And he said to him, "Why do you ask me about what is good? There is one who is good. If you would enter life, keep the commandments."
He said to him, "Which?" And Jesus said, "You shall not kill, You shall not commit adultery, You shall not steal, You shall not bear false witness, Honour your father and mother, and, You shall love your neighbour as yourself."
The young man said to him, "All these I have observed; what do I still lack?"
Jesus said to him, "If you would be complete, go, sell what you possess and give to the poor, and you will have treasure in heaven; and come, follow me."
When the young man heard this he went away sorrowful; for he had great possessions.
If you would enter life, keep the commandments. We all know that the answer to inheriting eternal life is not keeping the commandments. But that is what the young man believed. So I realized Jesus used the young man’s belief to bring him to the real way to eternal life — leave everything and follow Him. That is the only way.
Interestingly, Jesus' statement "If you would be complete, go, sell what you possess and give to the poor, and you will have treasure in heaven; and come, follow me." isn't exactly the same as His first one; He says "if you want to be complete" (teleios).
I realize the man had a problem with money that needed to be addressed, the young man is not my point of interest. My point is that if commandment keeping, under the law, was not a sign of faithfulness and a requirement for enjoying God's blessings on Israel, then it would seem that under the Old Covenant the people had no clear way of knowing this. The message seemed to be pounded into them over and over, "obey and live". And if we agree they were "saved by grace", just as we are, what are the implications for us?