וְלֹא־תוֹתִ֥ירוּ מִמֶּ֖נּוּ עַד־בֹּ֑קֶר וְהַנֹּתָ֥ר מִמֶּ֛נּוּ עַד־בֹּ֖קֶר בָּאֵ֥שׁ תִּשְׂרֹֽפוּ׃
And ye shall let nothing of it remain until the morning; but that which remaineth of it until the morning ye shall burn with fire.
Read kabbalistic (mystical) interpretation of Exodus 12:10: and classical mystical sources.