Guard against even the smallest theft
Among the wise advice and upright customs that Rav Dovid left in his Hanhagos Tovos is a grave warning to avoid theft, even of a shava peruta, the tiniest and most insignificant amount. Nothing that belongs to another person is too small to matter.
Source: Hanhagos Tovos of Rav Dovid of Stephin, printed in the Tzavaah of Rav Aharon of Karlin-Kingsberg and in Mayim Rabim