"Do this in memory of me."

Today is Holy Thursday in many Christian traditions and it is (at least in my faith tradition) commemorated with a remembrance of the Last Supper as well as ritualistic washing of the feet (though, not all parishioners get their feet washed - usually, just a few are preselected).

The Eucharistic celebration is an ancient Christian practice and some rules / guidelines are given for it in the Didache (or The Teaching of the Twelve Apostles). It is most commonly dated to have been composed in the early 2^nd century. Although some date it as early as 70 C.E.

CHAPTER 9 : eucharistic consecration

9:1 Now regarding the eucharist, give thanks in this way :
9:2 First concerning the cup :

"We thank You, our Father,
for the holy vine of David Your servant,
which You made known to us through Jesus Your servant.
To You belongs the glory for ever."

9:3 And concerning the broken bread :

We thank You, our Father,
for the life and knowledge which You made
known to us through Jesus Your servant.
To You belongs the glory for ever."

9:4 As this broken bread was scattered over the mountains, and was brought together to become one, so let Your church be gathered together from the ends of the earth into Your Kingdom, for the glory and the power are Yours through Jesus Christ forever.
9:5 But let none eat or drink of your eucharist except those who have been baptized in the Name of the Lord. For concerning this did the Lord say : “Give not what is holy to dogs.”

Taken from here because it is a nice English translation that does not suffer from burdensome use of stuffy anachronistic language.