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 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). Alternate 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)]