Eruvin, Chapter 7, Mishnah 6. The Mishnah explains how a "shituf mevo'os" is made - creating a partnership among all the courtyards that open into an alley, which allows the residents of those courtyards to carry within the alley.
"Keitzad mishtatfin bamavoi" - How does one make a shituf in an alley:
A shituf mevo'os need not be made specifically with bread; it may also be made with other foods and with beverages. Therefore one sets down a barrel - of wine, of oil, or of some other food - and declares that it belongs to all the residents of the alley. In order for them to acquire it, the acquisition is carried out through another person, who acquires the barrel on behalf of all the residents of the alley.
Who is fit to serve as the one who acquires it on their behalf:
"Beno u'vito hagedolim" - his grown son and daughter, provided they have reached the age of mitzvos. Ideally they should not be supported at his table, but rather financially independent; nevertheless, the acquisition is effective even if they are not financially independent, as long as they have reached the age of bar or bas mitzvah.
"Avdo v'shifchato ha'Ivrim" - his Hebrew manservant and maidservant, whose hand is not necessarily like his hand.
"Ishto" - his wife, and here there is a disagreement as to whether she must be financially independent.
And who is unfit for this acquisition?
"Beno u'vito haketanim" - his minor son and daughter, who have not yet reached the age of bar or bas mitzvah.
"Avdo v'shifchato ha'Kena'anim" - his Canaanite manservant and maidservant - "mipnei sheyadan k'yado" - because their hand is like his hand.
The underlying principle: for the acquisition to be effective, so that ownership of an object can be transferred to another person even in his absence, the object must leave the hand of the one transferring it. And all of these - the minors and the Canaanite slaves - their hand is like his hand, and therefore the object does not leave his hand at all.
In summary: In this Mishnah we learned how a shituf mevo'os is made, by setting down a barrel and declaring that it belongs to all the residents of the alley, and the law of acquiring on behalf of others: his grown son and daughter, his Hebrew manservant and maidservant, and his wife are all fit for this; but his minor sons and daughters and his Canaanite manservant and maidservant are unfit, since their hand is like his hand and the object never leaves his domain.