Reference for Chullin 9:29

Everyone is permitted to slaughter [an animal for non-consecrated purposes, see Hul. 1:1], even a Samaritan, even an uncircumcised Israelite, and even an Israelite who changes his belief to idolatry (lit., "worship of the stars"). The slaughter by an idolater, behold, that is invalid, and the slaughter by a monkey, behold, that is invalid, as it is said, "And you shall slaughter…and you shall eat” (Deut. 27:7). Not that "the idolater shall slaughter," and not that "the monkey shall slaughter," and not that the slaughter shall be accidental. An Israelite that [commenced the] slaughter, and an idolater finished the slaughter with his own hands, the slaughter is invalid. If he slaughtered two [simanim, the gullet and the windpipe, see Hul. 2:1], or the majority of two, his slaughter is valid. An idolater that [commenced the] slaughter, and an Israelite finished the slaughter with his own hands, the slaughter is valid. If [the idolater commenced the] slaughter with something that does not render [the slaughter] a tereifa (i.e., prohibited from consumption, see Hul. 3:1), and the Israelite came and finished, it is permitted to eat. An Israelite and an idolater that were holding the knife, and they slaughter -- even [if] one was on top and one was on the bottom (Hul. 2:2) -- their slaughter is valid.