"Thou shalt not steal." Exodus 20:15
This is probably the most straightforward of all the commandments. If its not yours don't take it. If you did not earn it don't take it. Do not use trickery or subterfuge to con someone into giving you something. Stealing is stealing, weather its through fraud, trickery, deceit, or force.
Israel in trouble
Joshua 7:10-26
And the LORD said unto Joshua, Get thee up; wherefore liest thou thus upon thy face? Israel hath sinned, and they have also transgressed my covenant which I commanded them: for they have even taken of the accursed thing, and have also stolen, and dissembled also, and they have put it even among their own stuff. Therefore the children of Israel could not stand before their enemies, but turned their backs before their enemies, because they were accursed: neither will I be with you any more, except ye destroy the accursed from among you. Up, sanctify the people, and say, Sanctify yourselves against to morrow: for thus saith the LORD God of Israel, There is an accursed thing in the midst of thee, O Israel: thou canst not stand before thine enemies, until ye take away the accursed thing from among you. In the morning therefore ye shall be brought according to your tribes: and it shall be, that the tribe which the LORD taketh shall come according to the families thereof ; and the family which the LORD shall take shall come by households; and the household which the LORD shall take shall come man by man. And it shall be, that he that is taken with the accursed thing shall be burnt with fire, he and all that he hath: because he hath transgressed the covenant of the LORD, and because he hath wrought folly in Israel. So Joshua rose up early in the morning, and brought Israel by their tribes; and the tribe of Judah was taken: And he brought the family of Judah; and he took the family of the Zarhites: and he brought the family of the Zarhites man by man; and Zabdi was taken: And he brought his household man by man; and Achan, the son of Carmi, the son of Zabdi, the son of Zerah, of the tribe of Judah, was taken.And Joshua said unto Achan, My son, give, I pray thee, glory to the LORD God of Israel, and make confession unto him; and tell me now what thou hast done; hide it not from me. And Achan answered Joshua, and said, Indeed I have sinned against the LORD God of Israel, and thus and thus have I done: When I saw among the spoils a goodly Babylonish garment, and two hundred shekels of silver, and a wedge of gold of fifty shekels weight, then I coveted them, and took them; and, behold, they are hid in the earth in the midst of my tent, and the silver under it.
So Joshua sent messengers, and they ran unto the tent; and, behold, it was hid in his tent, and the silver under it. And they took them out of the midst of the tent, and brought them unto Joshua, and unto all the children of Israel, and laid them out before the LORD. And Joshua, and all Israel with him, took Achan the son of Zerah, and the silver, and the garment, and the wedge of gold, and his sons, and his daughters, and his oxen, and his asses, and his sheep, and his tent, and all that he had: and they brought them unto the valley of Achor. And Joshua said, Why hast thou troubled us? the LORD shall trouble thee this day. And all Israel stoned him with stones, and burned them with fire, after they had stoned them with stones. And they raised over him a great heap of stones unto this day. So the LORD turned from the fierceness of his anger. Wherefore the name of that place was called, The valley of Achor, unto this day.