Deuteronomy 22:2
And if thy brother be not nigh unto thee, or if thou know him not, then thou shalt bring it unto thine own house, and it shall be with thee until thy brother seek after it, and thou shalt restore it to him again. And if thy brother be not nigh unto thee, or if thou know him not, then thou shalt bring it unto thine own house, and it shall be with thee until thy brother seek after it, and thou shalt restore it to him again.
When a fellow Israelite's lost animal or other stray belonging is found, and its owner is not nearby or is unknown, the finder must bring it to his own house and keep it there. It is to remain with him and be kept safely until the owner comes seeking after it, and then it must be restored to him again. This is the requirement for caring for a neighbor's lost property and returning it.
The duty to return stray property, or to keep it safe until it is claimed, stands in contrast to the law that forbids returning an escaped servant to his master. As part of the broader law of mercy in Deuteronomy 22:1-4, it shows that to fail to help a person in distress is to breach the duty to show mercy, as the priest and the Levite did when they failed to help.
The same neighborly care for another person's livestock implies that when livestock strays into a neighbor's grain, the neighbor should alert its owner or drive it out. Such an act may win the neighbor.