Be merry - Literally, "eating, let us rejoice." The word "merry" does not quite express the meaning of the Greek. "Merriment" denotes a light, playful, jovial mirth. The Greek denotes simply "joy - let us be happy, or joyful."

The fatted calf, and kill it - Θυσατε, Sacrifice it. In ancient times the animals provided for public feasts were first sacrificed to God. The blood of the beast being poured out before God, by way of atonement for sin, the flesh was considered as consecrated, and the guests were considered as feeding on Divine food. This custom is observed among the Asiatics to this day.

And bring hither the fatted calf, and kill it,.... By which Christ is designed, in allusion to the calves offered in sacrifice, which were offered for sin offerings, and for peace offerings, and for burnt offerings; and were one of the sacrifices on the day of atonement: so Christ has offered up himself in soul and body, freely and voluntarily, in the room and stead of his people, an offering and sacrifice to God, of a sweet smelling savour; which is well pleasing to him, and effectual to the purposes for which it was offered, and therefore will never be repeated; and has hereby satisfied law and justice, procured peace and reconciliation, and made full atonement and expiation for all their sins and transgressions: or else in allusion to the feasts and liberal entertainments of friends, when the fatted calf made a considerable part, Genesis 18:7 Christ is the best provision that can be set before a believer, or he can feed upon; yea, the best that God can give, or saints desire: he is true and real food, spiritual, savoury, satisfying, and durable; what both gives and preserves life; nourishes, strengthens, refreshes, delights, and fattens. Now by "bringing it hither", is meant preaching Christ; opening the Scriptures concerning him; setting him before believers, as their only proper food, both in the ministry of the word, and in the Lord's supper: and "killing" him does not design either the slaying of him in purpose, promise, and type, from the foundation of the world; nor the actual crucifixion of him by the Jews; but the setting him forth in the Gospel in a ministerial way, as crucified and slain, for saints by faith to feed and live upon:
and let us eat and be merry: for as the Jews (f) say,
"there is no mirth without eating and drinking:''
this is a mutual invitation or encouragement to eat of the fatted calf: the parties called upon to eat of it are the Father, the servants, and the returned son. The Father, to whom the salvation of his people, by the death of Christ, is as a feast; his heart was set upon this from everlasting; and he was infinitely well pleased with Christ, as the surety of his people from all eternity; his eye was upon him as such throughout the several dispensations before his coming; he sent him forth with great pleasure in the fulness of time; and not only did not spare him, but it even pleased him to bruise him; and he accepted of his sacrifice with delight; and takes pleasure in seeing his people feed upon their crucified Saviour; and this is expressive of that communion which God admits his people to with himself, and which, as it is signified by walking and talking, and sitting and dwelling, so by eating together; and is in consequence of union to him; and is only enjoyed by true believers; and is the greatest blessing on earth, and what is next to heaven. The servants, the ministers of the Gospel, they are among the "us", who are to eat; and it is but reasonable they should, and it is even necessary that they do eat, and live upon a crucified Christ themselves, whose business it is to set him forth as such to others: and especially the returned son makes a principal guest at this entertainment; for whom it is made, and for whose sake chiefly the invitation to eat is given: by which is meant not corporeal eating, but eating by faith; which supposes food to eat, of which there is plenty in the Gospel provision; a principle of life infused, for a dead man cannot eat; and spiritual hunger and thirst, otherwise there will be no appetite; and the grace of faith; which is the hand that takes, and the mouth that receives, and eats spiritual food: and believers have full and free liberty to eat of it; nor should they object their own unworthiness, but consider the suitableness of the food unto them; that it is on purpose prepared for them; that they are in their Father's house, and at his table; and the invitation to eat is hearty and cordial; and both the Father and Christ give this food, and bid welcome to it; and there is a necessity of eating it, for without this there can be no living in a spiritual sense: it is hereby that life is supported and maintained; without this the saints must be starving; it is this which preserves from hunger, and satisfies it, and nourishes up unto eternal life. The manner of eating, or the circumstance attending it, is "mirth", both in Father, son, and servants; and as corporeal, so spiritual eating should be with joy, and with a merry heart, Ecclesiastes 9:7 and indeed is the most proper means of stirring and increasing spiritual joy and pleasure; see the note on the latter part of the following verse, See Gill on Luke 15:24.
(f) T. Bab. Moed Katon, fol. 9. 1.

the fatted calf--kept for festive occasions.

Let us be merry - Both here, and wherever else this word occurs, whether in the Old or New Testament, it implies nothing of levity, but a solid, serious, religious, heartfelt joy: indeed this was the ordinary meaning of the word two hundred years ago, when our translation was made.