In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Abu Hurairah (radiyallaahu-anhu) said: “One of you looks at the mote in his brother’s eye while forgetting the stump in his own eye.” [Ref: 1]
This narration shows that it is obligated on (a person) to pre-occupy himself with his own faults (or shortcomings) before looking at that of others. It is a severe heedlessness that a Muslim becomes heedless of his faults and delays rectification of himself, yet he criticises others and even though his faults are more and greater than that of others. Therefore what is obligated on a Muslim and a Muslimah is to strive to prevent oneself from violating Allaah’s commands and prohibitions. Also, one should strive to call others to the (path of) Allaah, so that they are distanced from sins- because sins are a heavy burden on a person in this life and the next- and make them incline towards obedience to Allaah, which will make their scales of good deeds heavy, earns a person paradise and the pleasure of Allaah, and saves him from the Anger of Allaah and His painful punishment.
However, it must be borne in mind that warning against ahlul bidah – those who call to their bidah by way of speech and books-is not tantamount to seeking after the faults (or shortcomings) of others, for indeed to warn against ahlul bidah is an established Sunnah- obligated by the Qur’an and the Sunnah. That is because to abandon the mention of a Mubtadi in order to warn against him is tantamount to abandonment of [Amr Bil Ma’roof Wan-Nahy Anil Munkar – Enjoining Good and Forbidding Evil]. Therefore, we must make a distinction in order to know what is commanded and what is prohibited, and the difference between warning against [innovators, innovations] and the (blameworthy act) of seeking after the faults of others. [Awnul Ahadis Samad Sharh Al-Adab Al-Mufrad’ Vol 2 page 205′ by Shaikh Zayd Bin Haadi (rahimahullaah). Slightly paraphrased]
[Ref 1: Imaam Albaani (rahimahullaah) stated (in As-Saheehah 1/74-75) about this Hadeeth: ‘Saheeh Mawqoofan’.