Parsha Quiz - once in 50 yrs. ?

There was a unique Mitzva once in 50 years on Yovel. This Mitzva overrides even Shabos if it comes out on that Yom kippur. Which Mitzva ?

It is the shofar blowing to free all Jewish slaves. 25:9. Mitzva 331.
Now may be a good time for a gem of Torah study.
www.GemsofTorah.com