Boyd’s Bible Dictionary:
Punishment of theft was severe under the Mosaic law, as in all pastoral countries where the property was chiefly in flocks, more or less exposed to persons of felonious intent
The thief was compelled to make restitution, five-fold for a stolen ox and fourfold for a sheep. To kill a thief, caught in the act, was not a capital offense. If restitution was impossible a thief could be sold (Ex. 22:1-4).
Concise Bible Dictionary:
1. ληστής “robber, bandit.” Used by the Lord in reference to those who bought and sold in the temple (Matt. 21:13; Mark 11:17; Luke 19:46). In the parable of the Good Samaritan the traveler fell among robbers (Luke 10:30, 36). When the Lord was arrested He asked if they had come out as against a robber (Matt. 26:55; Mark 14:48; Luke 22:52). The two malefactors crucified with the Lord were also men of this character (Matt. 27:38,44; Mark 15:27). The same Greek word is translated “robber” in the AV in John 10:1, 8; John 18:40; and 2 Cor. 11:26.
2. κλέπτης, “thief.” Those who break through and steal secretly (Matt. 6:19-20). This is the word employed in the expression “as a thief in the night,” to which the unexpected coming of the Lord to the world is compared (1 Thess. 5:2,4; 2 Pet. 3:10; Rev. 3:3). It is applied to Judas (John 12:6). The word “thief” in the AV is always this word except in the passages quoted under No. 1.