When a Festival occurs on Thursday or Friday, one should [make an Eruv Tavshilin on the day preceding the Festival. This is done by taking Matzah prepared for Shabbat as well as a highly regarded cooked food, such as meat or fish, hand it over to another person through whom he grants a share of this Eruv to the entire community. Eruv Tavshilin
The one who makes the Eruv says:
I hereby grant a share in this Eruv to anyone who wishes to participate in it and to depend upon it.
The one to whom the bread and food was handed raises them a tefach (handsbreadth) and then returns them to the one making the Eruv, who recites the following:
Blessed are You, L-rd our G-d, King of the universe, who has sanctified us with His commandments, and commanded us concerning the Mitzvah of Eruv.
(Amen is answered by the listener). He continues to recite:
Through this it shall be permissible for us to bake, to cook, to put away [a dish to preserve its heat], to kindle a light, and to prepare and do on the Festival all that is necessary for the Shabbat - for us and for all Israelites who dwell in this city.