Mar 7:12 And you suffer him no more to do ought for his father or his mother;
Alternative: And no longer send him away doing nothing for his father and mother.

Christ's message here is that the religious leaders tolerated someone in the community who violated the commandment of honoring their father and their mother if they gave their property as a gift to the temple. They should have shunned such a person, but didn't.

If the original KJV seems a little convoluted in saying that, it seems to be because the original translators have a problem with a specific word. I know nothing of ancient Greek except a little I learned in high school and what I have picked up over the years studying the Greek of Christ's words, so I am in no position to criticize the scholars who translated the NT into English in the KJV, but it sometimes feels like they tied themselves into knots because they wanted certain words to mean certain things even when they really didn't.

In this case, the problem word is, as it so often is, aphiêmi, which is the basis for all references of "forgiving sin" in the NT. However, it actually has the meaning, as you can see below, of getting rid of something, letting it go, sending it away. When Christ referred to "forgiving sin" he was really telling us to let go of our own mistakes and the mistakes of others and to get past them (another meaning of aphiêmi). This has much more the sense of not dwelling on the past and especially of letting go and leaving behind than any sense of absolution that the word "forgive" carries.

The idea of "suffering" the sins of another is very closely connected to the idea of "forgiving" their sins, at least in the older English of the KJV, but you see how maintain that idea forces the translators to mistranslate another word, in this case, oudeis. Here they translate it as "ought" when it actually means "naught" and "nothing." It is a negative world and has no sense at all of obligation.

"You suffer" is from aphiêmi (aphiemi), which means "to let fall," "to send away," "to let loose," "to get rid of," "to leave alone," "to pass by," "to permit," and "to send forth from oneself." This is the same word that is translated as "leave" and "forgive" in the New Testament.

"No more" is from ouketi (ouketi), which means "no more," "no longer," "no further" and generally, "not now."

"Ought" is from oudeis, (oudeis) which means "no one," "not one," "nothing," "naught," "good for naught," and "no matter."

"To do" is from poieô ( poieo), which means "to make," "to produce," "to create," "to bring into existence," "to bring about," "to cause," "to render," "to consider," "to prepare," "to make ready," and "to do."