What does "use the entire source" mean?
Both the Old Covenant revealings and the New Covenant revealings.
For example:
Jesus said, Matthew 15:17 "Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught?"
And Jesus said, Matthew 15:11 "Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man."
But Jesus also said:
Matthew 5:17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.
20 For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.
Now that would be very confusing to one who has no understanding of that Old Law Covenant. Which, believe it or not, most Jews don't really understand that Old Law Covenant today. They think they do, but because they leave of the spirit of the New Covenant, they cannot even understand the very Law Covenant their ancestors were a part of. They don't get that understanding handed down to them by means of their verbal opinions and traditions, for those are but the interference of their flesh trying to interpret that Old Law for themselves. If they really would understand that Old Law they need to allow Jesus and his disciples to explain it to them, but they are no more willing to do that today than were in the first century or for that matter than they have ever been. For they have always ignored the counsel of God's prophets in favor of seeing things as they desired to see them by means of what they believed was their own righteousness.
Romans 10:2-3 "For I bear them record that they have a zeal of God, but not according to knowledge. For they being ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God."
And we still find a huge number of Christians who trust in the word of Jews, oblivious to the ignorance of God's righteousness they are placing their trust in.
Some would even object to what I have just said, claiming that the fact they fell short of knowing God's righteousness does not mean they did not know their Law.
How foolish can they be? God's righteousness was the spirit of that Old Law. If they did not know God's righteousness it was impossible for them to really know that Old Law. And so what one gets apart from understanding God's righteousness in that Law, is a highly twisted understanding of that Old Law.
Even Jehovah's Witnesses fail in this regard.They have adopted the idea that the commandments to abstain from eating certain meats was for reasons of a physical health code. There are far too many inconsistencies with that theory. And the NWT mistranslates Deuteronomy 12:15 in an effort to force their incorrect view on the words of the Law, as do many others, all because they are inept of understanding.