Exodus 23:18

לא תזבח על חמץ וגו׳ means, you shall not sacrifice the Passover-lamb on the fourteenth day of Nisan before you have removed the leavened bread from your house (Mekhilta). (This verse is to be connected with v. 15). ולא ילין חלב חגי NEITHER SHALL THE FAT OF MY SACRIFICE REMAIN away from the altar (cf. the Targum). UNTIL MORNING. One might think, however, that the meaning is, that it shall not remain overnight on the altar and that the sacrifice would therefore become invalid even through the fat remaining overnight on the “wood-pile” of the altar! Scripture, however, states, (Leviticus 6:2) “[This is the law of the burnt-offering; it is that which may go up] on the fire-place of the altar all the night, [any time until the morning]”(Mekhilta), — Therefore the statement ולא ילין means, that this law of leaving the fat away from the altar overnight is infringed only if it has not been placed on the altar by the dawn of the morning, for it says, “[neither shall the fat remain] until morning”, but any time during the whole night one may lift it up from the pavement on to the altar (cf. Megillah 20b).

לֹֽא־תִזְבַּ֥ח עַל־חָמֵ֖ץ דַּם־זִבְחִ֑י וְלֹֽא־יָלִ֥ין חֵֽלֶב־חַגִּ֖י עַד־בֹּֽקֶר׃

Thou shalt not offer the blood of my sacrifice with leavened bread; neither shall the fat of my sacrifice remain until the morning.