Partly, because they were all obliged not to go out of the house till the morning, Exodus 12:22, and to leave none of it till that time, Exodus 12:10; partly, lest it should be either superstitiously or profanely abused; and partly, to signify that Christ and salvation are not to be had out of God's house or church. To take out and eat the marrow of it. This was required, partly to mind them of their hasty departure out of Egypt, wherein they had no leisure to break and empty the bones; and principally, that it might be an evident type of the Lord Jesus, in whom this was literally fulfilled, 1 Thessalonians 19:36. The bones were burnt with the other remainders of the lamb.
Related Commentaries of Exodus 12:46
Exodus 12:46
46 In one house shall it be eaten; thou shalt not carry forth ought of the flesh abroad out of the house; neither shall ye break a bone thereof.