τὸ ἀφύλακτον

From LSJ

ὃ σὺ μισεῖς ἑτέρῳ μὴ ποιήσεις → don't do to others what you don't want them to do to you

Source

Greek > English (Woodhouse)

being off one's guard, want of precaution, want of vigilance

Spanish

descuido