AN 2.9
PTS: A i 51
Lokapala Sutta: Guardians of the World
translated from the Pali by
Thanissaro Bhikkhu
Alternate translation: Ireland
This sutta (plus a concluding series of verses) also appears at Iti 42.

"Monks, these two bright qualities guard the world. Which two? Conscience & concern.[1] If these two bright qualities did not guard the world, there would be no recognition of 'mother' here, no recognition of 'mother's sister,' 'uncle's wife,' 'teacher's wife,' or 'wife of those who deserve respect.' The world would be immersed in promiscuity, like rams with goats, roosters with pigs, or dogs with jackals. But because these two bright qualities guard the world, there is recognition of 'mother,' 'mother's sister,' 'uncle's wife,' 'teacher's wife,' & 'wife of those who deserve respect.'"

Notes

1.
Concern for the results of unskillful actions.

See also: AN 7.6.