Albert Barnes Commentary Leviticus 6:28

"But the earthen vessel wherein it is boiled shall be broken; and if it be boiled in a brazen vessel, it shall be scoured, and rinsed in water." — Leviticus 6:28 (ASV)

The earthen vessel — Unglazed pottery would absorb some of the juices of the meat; and a vessel made holy could not be put to any other purpose.