It is forbidden to steal, as it says "You shall not steal".¹ A thief must pay double; and if he steals an ox or sheep and sells it (or gives it away) or slaughters it he pays for five oxen or four sheep [as it says "If a man steals an ox or sheep and slaughters it or sells it he shall pay five cattle in place of the ox and four sheep in place of the sheep... if the theft is found in his hands... he shall pay two"].² If the theft is intact he must return it; if not, he pays for it. Double payment applies only to real, movable property that belongs to an individual, as it says "For an ox, for an ass, for a sheep, for a garment... he shall pay double to his friend".^3,a

It is forbidden to buy stolen goods from a thief. If one does so and the thief is caught the buyer must return the goods to the owner (unless the owner had given up hope), but the owner compensates him and collects from the thief. If he bought from a known thief, however, he must return the goods to the owner (or pay for them, if the owner had given up hope) and collect from the thief.^b

We are commanded to keep accurate scales, weights and measures, as it says "You shall have just scales, just stones, a just dry measure and a just liquid measure".⁴ It is forbidden to keep inaccurate ones in our possession even if we do not use them, as it says "There shall not be in your pocket a large stone and a small stone...".⁵ It is forbidden to cheat someone by the use of false measure, as it says "You shall not do injustice in measure, weight or volume"⁴; and if one does so he must pay. There is a special prohibition against stealing land in the land of Israel by moving boundary markers, as it says "You shall not push back your friend's border... in the inheritance that you inherit..."^6,c

It is forbidden to kidnap, as it says "You shall not steal",¹ and it says "If a man is found stealing a person of his brethren of the children of Israel and he enslaves him and sells him, that thief shall die",⁷ and it says "And one who steals a man and sells him... shall die".^8,d

If a thief is caught in the act it is permitted to kill him unless it is certain that he would not have killed anyone who tried to stop him, as it says "If the thief is found in the tunnel and is struck and dies he has no blood-rights...".^9,e

Sources:
1. Ex. 20:15, Lev. 19:11, Deut. 5:17	a. 1:1,4,6,12; 2:1-2,10
2. Ex. 21:37; 22:3	b. 5:1-3
3. Ex. 22:8	c. 7:1-3,11;:8:1
4. Lev. 19:35-36	d. 9:1-2
5. Deut. 26:13-15	e. 9:7-10
6. Deut. 19:14
7. Deut. 24:7
8. Ex. 21:16
9. Ex. 22:1-2