The Talmud, by Joseph Barclay, , at sacred-texts.com
1. Three men who have eaten together are bound to bless after food. "If a person have eaten of that which is doubtful, whether it has paid tithe or not; or of first tithe from which the heave offering has been taken; or of second tithe or consecrated things, which have been redeemed; also, if the waiter have eaten the size of an olive; or a Samaritan be of the party?" "The blessing must be said." "But if one have eaten the untithedor first tithes from which the heave offering has not been takenor consecrated things which are unredeemed; or if the waiter have eaten less than the size of an olive, or a stranger be of the party?" "The blessing is not to be said."
2. There is no blessing at food for women, slaves, and children. What quantity is required for the blessing at food? The size of an olive. R. Judah says "the size of an egg."
3. "How do we bless at food?" "If there be three, one says, "Let us bless," etc.; if three and himself, he says, "Bless ye," etc.: if ten, he says, "Let us bless our God," etc.; if ten and himself, he says, "Bless ye," etc.; (so) if there be ten or ten myriads. If there be an hundred, he says, "Let us bless the Lord our God," etc.; if there be an hundred and himself, he says, "Bless ye," etc.: if there be a thousand, he says, "Let us bless the Lord our God, the God of Israel;" if there be a thousand and himself, he says, "Bless ye," etc.: if there be a myriad, he says, "Let us bless the Lord our God, the God of Israel, the God of Hosts, who sitteth between the Cherubim," etc.; if there be a myriad and himself, he says, "Bless ye," etc. etc. As he pronounces the blessing, so they respond after him, "Blessed be the Lord our God, the God of Israel, the God of Hosts, who sitteth between the Cherubim, for the food we have eaten." R. José the Galilean says they should bless according to the number of the assembly; for it is written, "Bless ye God in the congregations; (even) the Lord from the fountain of Israel." 1
[paragraph continues] Said R. Akivah, What do we find in the synagogue? whether many or few the minister says, Bless ye the Lord, etc. R. Ishmael says, Bless ye the Lord, who is ever blessed.
4. When three have eaten together, they are not permitted to separate without blessing; nor four or five. But six may divide into two parties, and so may any number up to ten. But ten may not separate without blessing, nor any number less than twenty (who can divide into two parties).
5. If two companies have eaten in one house, and some of each company be able to see some of the other company, they may join in the blessing; but if not, each company blesses for itself. "They should not bless the wine till it has been mixed with water." The words of R. Eleazar. But the Sages say "they may bless it unmixed."
58:1 Ps. lxviii. 26.