Umar bin al-khattaab: “If you see that one of you has slipped (i.e. by sins), correct him, pray for him and do not help Shaytaan against him (by insulting him, etc.)” Tafseer al-Qurtubi, 15/256.
Hasan al-Basri (d.110 A.H.) said:
‘Statements cannot be correct except with actions; Statements and actions cannot be correct except with an intention; and statements, actions and an intention cannot be correct except according to the Sunnah.’
[From ‘Sharh Usool I’tiqaad Ahl-us-Sunnah’ al –Laalkaee 2/57]