Charles Ellicott Commentary Exodus 12:9

"Eat not of it raw, nor boiled at all with water, but roast with fire; its head with its legs and with the inwards thereof." — Exodus 12:9 (ASV)

His head with his legs ... —The lamb was to be roasted whole: not a bone of it was to be broken (Exodus 12:46). Justin Martyr says that it was prepared for roasting by means of two wooden spits, one perpendicular and the other transverse, which extended it on a sort of cross, and made it aptly typify the Crucified One.

The purtenance thereof. —Hebrew: its inside. The entrails were taken out, carefully cleansed, and then replaced.