Mark 10:19 "You know the commandments: 'Do not murder, do not commit adultery, do not steal, do not give false testimony, do not defraud, honor your father and mother.'"
Some have objected that Jesus has altered one of the Decalogue commandments, changing it from "Do not covet" to "Do not defraud".
This "alteration", however, is nothing more than a rabbinic type of teaching within the parameters of Judaism. The rich, like the young ruler to whom Jesus was speaking, expressed covetousness concretely by means of defrauding. Jesus' choice of words reflects acceptable rabbinic practice.
Those who cite of Deut. 4:2 [forbidding adding to or changing the law] do not account for the fact that it is not "adding to or changing" to interpret or perform a didactic expansion. Moreover, even if it were, God, as the sovereign who has imposed the Deuteronomic treaty, has in the context of Ancient Near Eastern law the right to reformulate the covenant as He so desires [and by extension, the right to assign a delegate (Jesus) to do so]).
To this Malina adds (The New Testament World, 129) that Josephus reports that in his day, it was considered forbidden to utter the "Ten Words" of the Decalogue. The commands could not be recited in full, nor explicitly; they could be written verbatim, but not repeated verbatim. To disguise or re-order the Decalogue, but using truncation of substitution, was simply a normal and accepted procedure. However, a well-educated Jew like the rich young ruler would still be able to fill in the gaps.
On the other hand, this phrase is not found in the Matthean and Lukan paralles, and is ommitted in many manuscripts of Mark. McHardy therefore suggests (Expository Times, Feb. 1996, p. 143) that the Greek phrase here, ouk aposteresei, was a type of margin note used to refer the reader to the relevant passage in the Septuagint that the Gospel parallels where the same word also appeared. The reference could therefore be the result of a copyist error, he supposes. However, we would prefer to use Malina's answer above, and say that Matthew and Luke simply truncated the longer list for readers who already knew the entire Decalogue and didn't need it repeated.
This leads also to the issue: Why did Jesus not quote all Ten Commandments? Previously I answered that those he left out -- having no God before God, sabbath observance, etc. -- were all able to be taken for granted within the context of one Jew talking to another. But Herzog in Jesus, Justice and the Reign of God [163f] has another idea.
In Jesus' time the poor were being substantially oppressed by people like this rich man. In essence such people dethroned Yahweh and "replace[d] him with the gods of the colonial occupiers" and so was serving an idol -- Mammon. Such people even broke the Sabbath rule, not by failing to observe it themselves, but by extracting so much from the poor that they had to work on the Sabbath to survive, thus keeping the Sabbath far from holy. If that is so, then the omission is for the same reason as the one remaining commandment: The "covet" command that is indeed missing.
Why? Jesus left it out intentionally, knowing well enough that this was the command the rich man was most likely to have a problem with. Leaving out the command was a chance to "fill in the gap" and see if the rich man would pick up on the omission (or change, if the text is valid) on his own. If he said, "Yeah, I'm good on those, but also on coveting." it would have shown him to be indeed obedient. His inability to fill the gap (of perhaps even the five commandments) exposed his true nature.