What are the ramifications of the sun shining on the Ganav?
Rashi and Targum Yonasan: It is a Mashal that if it is as clear as daylight that if the Ba'al ha'Bayis confronts him, the Ganav will not kill him - such as a father who is stealing from his son - then the Ba'al ha'Bayis is not permitted to kill him.
Rashbam: If he comes to steal during the day, 1 whoever kills him is guilty of shedding blood.
Rashi citing Targum Onkelos: If witnesses see the Ganav, and when the Ba'al ha'Bayis comes, they warn him that if he kills [the Ganav], he will be liable for him, there is liability for him. Since witnesses see [and recognize] him, the Ganav does not intend to kill the owner. 2
Ramban (citing Onkelos): If the Ganav left the tunnel, and the Ba'al ha'Bayis says that he has witnesses that he was in the tunnel, he is liable if he kills him. Normally, a thief tunnels in at night, and if daylight comes, he flees. Witnesses can obligate him to pay for his theft, but Beis Din or the Ba'al ha'Bayis may not kill him.
Da'as Zekenim: If he comes during the day, he must pay for what he takes. 3
Since he comes to steal during the day, he is less afraid and is not therefore prone to kill. (EC). See also Ba'al ha'Turim.
See Ramban's objection to this explanation, and who explains that both the previous Pasuk and this one are speaking whether or not there are witnesses and warning. See also Rav Chavel's footnotes.
For Kam Lei bid'Rabah Minei does not apply (PF).
What does the second half of the Pasuk follow on from the first?
Rashi and Targum Yonasan: If, in the latter case (where, knowing that that the Ganav will not kill him) the owner does not kill him, he is Chayav to pay for whatever he stole (or damaged) in the process; 1 otherwise Beis-Din sell him. 2
Ramban: It doesn't! It follows on from "Ki Yignov" (in Shemos 21:37).
In the former case, where we suspect that he came with the intention of killing, he is Patur from paying Mamon - due to the principle 'Kam Lei bid'Rabah Minei' (a person who performs an act for which he is Chayav both Misah and Mamon, receives the stricter punishment, and is absolved from the more lenient one).
Why must a Ganav who is unable to pay be sold as an Eved?
Seforno: Because otherwise, the poor people will steal indiscriminately, knowing that, since they are unable to pay for the theft, they will get off scot-free.
What does "bi'Gneivaso" exclude?
Sotah 23b: A woman is not sold for her theft.
Kidushin 18a: One is sold to pay for his theft, but not to pay the Kefel, and not [Edim Zomemin who must pay] Ka'asher Zamam. 1
Moshav Zekenim: R. Eliyahu of Paris derived similarly 'not for his obligation', so a man need not hire himself out to work to feed his wife. R. Tam asked that the Kesuvah says 'I will work [and honor feed you]'! R. Eliyahu said, this refers to bodily honoring her. The Halachah follows R. Tam; this is not called a sale.