Tirukkural-On Virtue-Avoiding Slander-Kural 186

It is well for the slanderer, before he dwells on other's faults,To realize that his own select sins too, provide matter for slander.

This interpretation is based on Parimelalagar and Manakudavar, but Parithiar would say that before indulging in slander it is good to consider the worst one's won faults.

The latter is straightforward; but the former is more effective, being a little ingenious. Before one indulges in slander regarding other people's faults, it were certainly better for one to realize that his won choice faults would provide very 'juicy matter for slander by others.

The following passage of the Bible is relevant in this context:

'Thou, hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother's eye'.

(Matt. 7:5)

Cf. Kural 190.