The Sacrament of the Altar
As the head of the family should teach it in a simple way to his household.
What is the Sacrament of the Altar?
It is the true body and blood of our Lord Jesus Christ, under the bread and wine, for us Christians to eat and to drink, instituted by Christ Himself.
Where is this written?
The holy Evangelists, Matthew, Mark, Luke, and St. Paul, write thus:
For I received from the Lord what I also delivered to you, that the Lord Jesus on the night when he was betrayed took bread, and when he had given thanks, he broke it, and said, “This is my body which is for you. Do this in remembrance of me.
In the same way also he took the cup, after supper, saying, “This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me.” For as often as you eat this bread and drink the cup, you proclaim the Lord's death until he comes.
(1. Cor. 11:23-26, ESV)
What is the benefit of such eating and drinking?
That is shown us in these words:
Given, and shed for you for the forgiveness of sins
Namely, that in the Sacrament forgiveness of sins, life, and salvation are given us through these words. For where there is forgiveness of sins, there is also life and salvation.
How can bodily eating and drinking do such great things?
It is not the eating and drinking, indeed, that does them, but the words which stand here, namely: Given, and shed for you, for the forgiveness of sins. Which words are, beside the bodily eating and drinking, as the chief thing in the Sacrament; and he that believes these words has what they say and express, namely, the forgiveness of sins.
Who, then, receives such Sacrament worthily?
Fasting and bodily preparation is, indeed, a fine outward training; but he is truly worthy and well prepared who has faith in these words: Given, and shed for you, for the forgiveness of sins.
But he that does not believe these words, or doubts, is unworthy and unfit; for the words For you require altogether believing hearts.
(Go deeper with The Large Catechism - Sacrament of the Altar)