The blood of my sacrifice - It is generally considered that this must refer to the Paschal Lamb. See Exodus 12:7, Exodus 12:11, Exodus 12:13, Exodus 12:22-23, Exodus 12:27.

The fat of my sacrifice - Strictly, the fat of my feast; the "best part" of the feast, that is, the Paschal lamb itself. Compare Exodus 34:25.

The blood of my sacrifice with leavened bread - The sacrifice here mentioned is undoubtedly the Passover; (see Exodus 34:25); this is called by way of eminence My sacrifice, because God had instituted it for that especial purpose, the redemption of Israel from the Egyptian bondage, and because it typified The Lamb Of God, who taketh away the sin of the world. We have already seen how strict the prohibition against leaven was during this festival, and what was signified by it. See on Exodus 12 (note).

Thou shall not offer the blood of my sacrifice with leavened bread,.... This belongs to the feast of the passover; for, as all the Jewish writers agree, this sacrifice is the sacrifice of the passover, as it is sometimes called, see Exodus 12:27 now when the paschal lamb was killed, and its blood shed, and its flesh eaten, there was to be no leaven along with it; it was to be eaten with unleavened bread, and there was to be no leaven in their houses at this time; nay, it was not to be slain until all was removed: this was the first thing the Jews did, as soon as the fourteenth day was come, to search for leaven, remove and burn it; and this sense of the law is confirmed by the Targum of Jonathan, which is,"not a man shall slay, while there is leaven in your houses, the sacrifice of my passover;''and to the same purpose is the note of Jarchi:

neither shall the fat of my sacrifice remain until the morning; and indeed no part of the passover lamb was to remain until the morning, what did was to be burnt with fire, Exodus 12:10 the Targum of Jonathan is,"neither shall there remain without the altar the fat of the sacrifice of my passover until the morning, nor of the flesh which ye ate in the evening;''and so Jarchi interprets it of its not remaining without the altar.

The blessing attending their appearing before the Lord was dependent upon the feasts being kept in the proper way, by the observance of the three rules laid down in Exodus 23:18 and Exodus 23:19. "Thou shalt not offer the blood of My sacrifice upon leavened bread." על upon, as in Exodus 12:8, denoting the basis upon which the sacrifice was offered. The meaning has been correctly given by the early commentators, viz., "as long as there is any leavened bread in your houses," or "until the leaven has been entirely removed from your houses." The reference made here to the removal of leaven, and the expression "blood of My sacrifice," both point to the paschal lamb, which was regarded as the sacrifice of Jehovah κατ̓ ἐξοχήν, on account of its great importance. Onkelos gives this explanation: "My Passover" for "My sacrifice." - "Neither shall the fat of My feast remain (ילין to pass the night) until the morning." "The fat of My feast" does not mean the fat of My festal sacrifice, for חג, a feast, is not used for the sacrifice offered at the feast; it signifies rather the best of My feast, i.e., the paschal sacrifice, as we may see from Exodus 34:25, where "the sacrifice of the feast of the Passover" is given as the explanation of "the fat of My feast." As the paschal sacrifice was the sacrifice of Jehovah par excellence, so the feast of the Passover was the feast of Jehovah par excellence. The expression "fat of My feast" is not to be understood as referring at all to the fat of the lamb, which was burned upon the altar in the case of the expiatory and whole offerings; for there could have been no necessity for the injunction not to keep this till the morning, inasmuch as those parts of every sacrifice which were set apart for the altar were burned immediately after the sprinkling of the blood. The allusion is to the flesh of the paschal lamb, which was eaten in the night before daybreak, after which anything that remained was to be burned. עד־בּקר (without the article) till morning, has the same meaning as לבּקר "for the (following) morning" in Exodus 34:25.

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

(k) No leavened bread will be in your house.

sacrifice: or, feast

23:10-19 Every seventh year the land was to rest. They must not plough or sow it; what the earth produced of itself, should be eaten, and not laid up. This law seems to have been intended to teach dependence on Providence, and God's faithfulness in sending the larger increase while they kept his appointments. It was also typical of the heavenly rest, when all earthly labours, cares, and interests shall cease for ever. All respect to the gods of the heathen is strictly forbidden. Since idolatry was a sin to which the Israelites leaned, they must blot out the remembrance of the gods of the heathen. Solemn religious attendance on God, in the place which he should choose, is strictly required. They must come together before the Lord. What a good Master do we serve, who has made it our duty to rejoice before him! Let us devote with pleasure to the service of God that portion of our time which he requires, and count his sabbaths and ordinances to be a feast unto our souls. They were not to come empty-handed; so now, we must not come to worship God empty-hearted; our souls must be filled with holy desires toward him, and dedications of ourselves to him; for with such sacrifices God is well pleased.