Gemara

55b (Beraisa - R. Yehoshua): One who hired false witnesses is exempt b'Yedei Adam (Beis Din cannot make him pay), and liable b'Yedei Shamayim.

56a: One might have thought that he is exempt even b'Yedei Shamayim, for he can say 'they should have obeyed the Rav (Hash-m), and not the Talmid (me)!'

59b (Mishnah): If Levi sent a fire with a deaf-mute, lunatic or minor, and they damaged, Levi is exempt b'Yedei Adam, but he is liable b'Yedei Shamayim. If he sent a proper adult, the adult is liable.

Kidushin 42b: We do not attribute the Shali'ach's action to Levi, for the Shali'ach should have obeyed the Rav, and not the Talmid!

Bava Metzia 10b - Question: Reish Lakish holds that a Chatzer acquires like one's Shali'ach. A Beraisa obligates a thief if the stolen object is found in his Chatzer. We hold that Ein Shali'ach l'Devar Aveirah!

Answer #1 (Ravina): Ein Shali'ach l'Devar Aveirah only when the Shali'ach is Bar Chiyuva (liable for transgressing).

Answer #2 (Rav Sama): Ein Shali'ach l'Devar Aveirah only when the Shali'ach can choose whether or not to comply.

They argue about a Kohen who told a Yisrael 'be Mekadesh a divorcee to me', or a man who told a woman 'cut a boy's sideburns for me'. Since they can choose whether or not to obey, Rav Sama holds that the one who told them is not liable for their actions. Since they are not Bar Chiyuva for these actions, Ravina obligates the one who told them for their actions.

Rishonim

Rif and Rosh (Kidushin 16b and 2:2): Actions of David's Shali'ach are attributed to David, unless he was told to do an Aveirah. Then, we say that he should have listened to Hash-m, not to David.

Rif and Rosh (Bava Kama 29a and 7:9): In the entire Torah, Ein Shali'ach l'Devar Aveirah, except for a thief who made a Shali'ach to sell or slaughter.

Rambam (Hilchos Me'ilah 7:2): In the entire Torah, Ein Shali'ach l'Devar Aveirah, except for Me'ilah with no other Isur involved.

Rosh (Bava Metzia 1:30, and Nimukei Yosef 5b DH Garsinan citing the Ran): The Ramah says that the Halachah follows Rav Sama. Since he said his Halachah in front of Ravina and Ravina was silent, this shows that Ravina retracted. Therefore, the only Shali'ach l'Devar Aveirah is a Chatzer.

Nimukei Yosef: A child who cannot acquire at all, e.g. he does not distinguish between a rock and a nut, is like a Chatzer to obligate one who sends him. We cannot say 'the child chooses whether or not he will do so.'

Rebuttal (Shach CM 182:1): Shelichus does not apply to minors! He is unlike a Chatzer, which is its owner's Reshus, and is his Shali'ach. If Levi sent a fire with a lunatic or minor, and they damaged, he is exempt b'Yedei Adam, but liable b'Yedei Shamayim. If he sent a proper adult, the adult is liable, for Ein Shali'ach l'Devar Aveirah. A child who cannot acquire is like a lunatic. Levi is exempt (b'Yedei Adam) because a lunatic cannot be a Shali'ach at all.

Nesivos ha'Mishpat (1): A minor is not a Shali'ach for his act to take effect, but he obligates the Meshale'ach (when Yesh Shali'ach l'Devar Aveirah).

Tosfos (56a DH Ela): One who hired false witnesses is liable b'Yedei Shamayim when the witnesses cannot pay. If he asked them to testify falsely for free, he is totally exempt, for he mid'Oraisa expect them to obey. One who sent a fire with a minor is liable b'Yedei Shamayim. One who sent an adult is totally exempt (59b)!

Shach (CM 32:3): The Ritva totally exempts the sender when the Shali'ach pays. Hash-m did not allow the serpent to claim that Chavah should have obeyed the Rav (Sanhedrin 29a), for this exempts even b'Yedei Shamayim!

Poskim

Rema (CM 182:1): In all matters, actions of David's Shali'ach are attributed to David, except for an Aveirah. We hold that Ein Shali'ach l'Devar Aveirah, when the Shali'ach is a Bar Chiyuva. If he is not, he is a Shali'ach even for an Aveirah.

SMA (2): The Meshale'ach can say 'I did not think that he would heed me to do it.' This does not apply when the Shali'ach is not Bar Chiyuv.

Hagahos Maimoniyos (Hilchos Sheluchim 2:1): In Bava Metzia, (we say that) when the Shali'ach is Bar Chiyuva, the Meshale'ach is exempt. If David told Levi 'take my ox from Ploni's house. It is mine', and it was found that it was not David's and he intended to steal, David is liable through the Meshichah of Levi. Since Levi did not know that it is stolen, he is like a Chatzer that people put things in it b'Al Korcho (against its will), even though Levi could choose whether or not to comply. (This is from) Perush Ri.

Darchei Moshe (1): We learn from here that Ein Shali'ach l'Devar Aveirah only when the Shali'ach is Bar Chiyuva, and knows that it is an Aveirah.

Rebuttal (Shach 1): Perhaps Hagahos Maimoniyos holds like Rav Sama, who says that Ein Shali'ach only when the Shali'ach can choose whether or not to comply. His initial words 'when the Shali'ach is Bar Chiyuva...' merely cite the Gemara he learns from. The Darchei Moshe (CM 348) cited the Mordechai to obligate the Meshale'ach when the Shali'ach is exempt. He did not say that anyone argues. It seems that also the Mordechai holds like Rav Sama. Hagahos Maimoniyos cited the Mordechai! Also the Rashba (1:571) explains according to Rav Sama, which connotes that he rules like him. The Rosh said that the Ramah rules like Rav Sama; it seems that he agrees. The Nimukei Yosef and Ran agree. The Rif wrote that Ein Shali'ach, and did not give exceptions, for he rules like Rav Sama. The only Shali'ach l'Devar Aveirah is a Chatzer. This applies only to Kefel, and we do not collect fines nowadays.

Note: Seemingly, a Chatzer could make one liable to pay for the theft if it later was lost, died or decreased in value. These are relevant even nowadays!

Shach (ibid.): Also, obviously he is liable through a Chatzer, for he puts in it b'Al Korcho. R. Yerucham says that Yesh Shali'ach when the Shali'ach is not Bar Chiyuva. It seems that this is a textual error. R. Yerucham usually rules like the Rosh. He would not rule unlike him without mentioning this! Also, he said that the only Shali'ach l'Devar Aveirah is a Chatzer. Even though those who rule like Rav Sama do so because Ravina heard his opinion and was quiet, and this is not in our texts, presumably our text is abbreviated. I saw an old text like that of the Rosh and Ran.

Support (Noda bi'Yehudah 75 DH v'Hinei): Rava taught about a Shali'ach to eat Chelev according to Shamai (Kidushin 43a). If Yesh Shali'ach when he is not Bar Chiyuva, Ravina would have taught according to Halachah! However, the Pnei Yehoshua (Tosfos DH she'Lo) explains that Rava's law is only when the Shali'ach is Bar Chiyuva; for then the Meshale'ach cannot also be liable.

Pischei Teshuvah (YD 160:16): Mahari Di Boton (168) says that if the Meshale'ach forced and intimidated the Shali'ach, (Yesh Shali'ach l'Devar Aveirah and) he is liable. The Sha'ar ha'Melech disagrees, for the Gemara (Bava Kama 51a) could not find a pit of partners in this way.

Rema (348:8): If Reuven showed David an item to steal, or sent him to steal it, Reuven is exempt, for Ein Shali'ach l'Devar Aveirah. However, if David is not Bar Chiyuva, some say that Reuven is liable.

Question (Darchei Moshe, ibid.): The Terumas ha'Deshen (315) says that if Reuven showed a known thief a tunnel from which to steal, this is Gerama in Nezikim, so Reuven is exempt. In any case he is exempt, for Ein Shali'ach!

Answer #1 (SMA): The Rema (in Siman 182 Stam, and here according to one opinion) obligates the Meshale'ach when the Shali'ach is not Bar Chiyuva. The Terumas ha'Deshen exempts even in such a case, for it is Gerama. And even if such a Shali'ach is exempt, showing a thief is not Shelichus. One who shows a Nochri is liable due to Garmi (a more severe form of Gerama for which R. Meir obligates). Here, it is only Gerama.

Answer #2 (Hagahos Drishah 1): Surely, a known thief will steal. One cannot say 'I did not think that he will do so, for he should have listened to Hash-m.'