An Eved and Eruvei Techumin — Eruvin 79b
תלמוד בבלי מסכת עירובין דף עט/ב
ואומר הרי זו לכל בני מבוי ומזכה להן על ידי בנו ובתו הגדולים ועל ידי עבדו ושפחתו העברים ועל ידי אשתו אבל אינו מזכה לא על ידי בנו ובתו הקטנים ולא על ידי עבדו ושפחתו הכנענים מפני שידן כידו
In a fascinating comparison, the Rogatchover (Tzofnas Pa'anei'ach, Mahadura Tinyana 33d) contrasts the law that Canaanite slaves are not capable of contracting eruvin with the law (Rambam, Hil. Klei Mikdash ) that broken klei shareis (holy vessels used in the Beis HaMikdash) that were melted and forged again remain holy.
In the introduction to Moreh Nevuchim (volume two, fourth introduction), the Givas HaMoreh distinguishes between sudden changes and gradual changes. The Rogatchover expands on this distinction, and asserts that abrupt changes indicate a change into a new entity, while gradual changes indicate that the entity retains at least some degree of its previous status.
The Rogatchover explains that this distinction underlies the difference between a convert and a slave in terms of the fulfillment of the mitzvah of pru u'revu. A ger's conversion is done with his intent and consent, while a slave's release is not done with his intent and consent. Thus, a ger's change in status is gradual while an eved's is abrupt. Hence, the children that a ger had before he converted count towards the mitzvah, while the children that an eved had before he was released do not count towards the mitzvah.
Similarly, the melting and forging of the broken klei shareis is gradual, and therefore the kli shareis retains its holiness. On the other hand, upon his release, the eved becomes a completely new entity. Extrapolating backwards, the Rogatchover concludes that an eved prior to his release has no legal identity. His capacity to eat from his master's korban pesach, or from the master's terumah if the master is a Kohen, is an extension of the master's status, not a function of his own.
A ramification of his lack of legal identity is that an eved does not need to have his own two meals when he participates in an eruv techumin with his master. In this respect, he is like a child, who is a part of his mother's eruv (below 82a).