Gemara

(Mishnah): If the ox of a Cheresh, lunatic or minor gored, Beis Din appoints an Apotropus (overseer). Witnesses testify in front of the Apotropus.

(Rava): This refers to an ox established to gore. Witnesses testify in front of the Apotropus to make the ox Mu'ad. Future gorings are paid for from the Aliyah (i.e., not from the ox itself).

(R. Yochanan): After it is Mu'ad, the minor pays.

(R. Yosi bar Chanina): The Apotropus pays.

(Rava): R. Yochanan says that we collect from the minor, for if we would collect from the Apotropus, no one would agree to be an Apotropus. R. Yosi bar Chanina says that we collect from the Apotropus. When the minor grows up, the Apotropus collects from him.

87a (Mishnah): Encounters with a Cheresh (deaf-mute), lunatic or minor are bad. One is liable if he damaged one of them, but if one of them damaged, he is exempt. Encounters with a slave or woman are bad. One is liable if he damaged one of them, but if one of them damaged, he or she does not pay now. He or she is liable after freedom or divorce.

98b: A case occurred, and Rafram forced Rav Ashi to pay the full value of a loan document that he burned.

112a (Beraisa): If one stole and fed his children, they are exempt. If he left the theft in front of them and they ate, whether they are adults or minors, they are liable.

Objection: Why are minors liable? This is no worse than damage, for which they are exempt!

Correction (Rav Papa): Rather, if he left the theft in front of them and they did not yet eat it, whether they are adults or minors, they are liable.

Bava Metzia 102a (Beraisa): If one finds a mother on eggs or chicks in a dovecote or an upper story, he must send the mother before taking her offspring. If he takes them, it is considered theft due to Darchei (the ways of) Shalom.

Question: If one's Chatzer acquires for him without his knowledge, he owns the eggs. He should not have to send the mother!

Answer: The Chatzer does not acquire them when the owner could not acquire them (i.e. while the mother is on them).

Question: If the mother was sent, the owner of the Chatzer acquires them, this is absolute theft, not merely due to Darchei Shalom!

Answer: A minor found the birds. He is not commanded to send the mother. His father must return the eggs due to Darchei Shalom.

Rishonim

Rif 31b: Encounters with a Cheresh, lunatic or minor are bad.

Nimukei Yosef (Bava Kama 19a DH Cheresh): The Reisha exempts for an ox of a Cheresh, lunatic or minor that gored. Just like these people do not pay for what they damaged, they do not pay for damage of their property. This is like Sumchus. Chachamim hold that we set up an overseer to avert future damage. We collect from the ox itself. We cannot set up an overseer to stop a minor from damaging. If we would collect from his property, it would be finished off. The ox can be watched, and if it is collected, the damage goes away. All agree that we set up an overseer to make it Mu'ad.

Rosh (Bava Kama 8:9): If a slave or woman damaged, he or she is liable after freedom or divorce. This is unlike a minor, who is not liable to punishment.

Or Zaru'a, in Hagahos Ashri: Rashi says that this is why Rafram forced Rav Ashi to pay. This shows that a minor is obligated to pay after he matures. Also, R. Yosi b'Ribi Chanina said that says when the minor grows up, the Apotropus collects from him for what his animal damaged (Bava Kama 39b). All the more so, after he matures he must pay for what he damaged!

Rebuttal (Bach OC 343 DH Ach): The Or Zaru'a must mean that even though mid'Oraisa he is exempt, Chachamim enacted that he must pay when he matures, for Tikun ha'Olam. This is like Tosfos (39a DH Ein), who says that it is an enactment to collect for damages of a minor's ox. The Poskim disagree with the Or Zaru'a. It is unusual for a minor to damage. Chachamim enacted only for damage of an ox, which is common. Indeed, Rav Ashi burned the document when he was a minor. (If he did so b'Shogeg or b'Ones, it would be no detriment to say that he did so in adulthood.) Letter of the law, he was exempt, but it is proper for Beis Din to lash minors. Rav Ashi did not want to suffer the lashes, therefore he paid the full damage. It is improper to say that after Rav Ashi matured he would defy Beis Din and need to be forced.

Taz (OC 343:2): Rafram verbally forced Rav Ashi to go beyond the letter of the law. We find that Rav ruled that Rabah bar bar Chanah must go beyond the letter of the law and pay workers who broke his barrel (Bava Metzia 83a).

Taz (CM 96:3): In Kesuvos, Rashi himself (86a DH Kafyei) explained differently (that a case came in front of Rav Ashi, and Rafram overwhelmed him with proofs, and forced him to collect due to Garmi). Also Bava Kama 112a proves that minors are exempt even after they mature.

Rambam (Hilchos Geneivah 1:8): If a minor stole, we return the stolen object. If he lost the object he is exempt, even after he matures.

Maharam Padava (90) and Taz (CM 348:3): The Rambam can explain that Rav Ashi burned a document when he was 13 years old. Rashi only said that it was in his youth, i.e. before he was a Chacham. When it says 'you taught to us in your youth', it does not mean before Bar Mitzvah! The Rambam learns from the Mishnah that says that encounters with a minor are bad. It says only regarding a slave or woman that they pay later, for they had Da'as.

Rambam (Hilchos Chovel u'Mazik 4:20): If a minor damaged, he is exempt, even after he matures, for he had no Da'as when he damaged.

Terumas ha'Deshen (62): The Rosh exempts a minor who wounded or damaged, even when he matures. Bahag obligates him when he matures.

Sefer Chasidim (692): If one remembers what he stole when he was a minor, he must pay, just like Yoshiyahu repented from all his Aveiros and paid for all his improper judgments. If a same person went crazy and regained sanity, he must pay for whatever witnesses say that he damaged.

Poskim

Shulchan Aruch (349:3): If a minor stole, he returns the principal to the owner if it is intact. If it is not intact he is exempt even after he matures.

Gra (2): We learn from Bava Metzia (if he sent the bird, it is absolute theft).

Shulchan Aruch (424:8): If a minor wounded he is exempt, even after he matures, for he had no Da'as when he damaged.