Humility makes us charitable toward our neighbor. Nothing will make us so generous and merciful to the faults of others as seeing our own faults.

François Fénelon (1651–1715) French Catholic archbishop, theologian, poet, writer [François de Salignac de la Mothe-Fénelon]

Letter, Undated [tr. Edmonson / Helms]
    (Source)

In Robert J. Edmonson, Hal M. Helms (eds.), The Complete Fénelon, Part 2, ch. 8 (2008). Other translations:

Nothing will make us so charitable and tender to the faults of others as by self-examination thoroughly to know our own.
[Source (1895)]

Humility renders us charitable towards our neighbor; nothing will make us so tender and indulgent to the faults of others as a view of our own.
[tr. Metcalf (1853)]