Sincerity cannot coexist in a heart that contains the love of praise and commendation and the yearning to possess that which is owned by the people save in the manner that fire and water or a lizard and fish may coexist.
If your soul directs you to seek sincerity then first turn your attention towards your yearning and slaughter it with the knife of renunciation. Then turn your attention towards praise and commendation and forsake it with the asceticism of those who loved the world for the sake of the Hereafter. When your slaughtering of your yearning and the renunciation of praise and commendation becomes firm then attaining sincerity will become easy for you.
If it is asked: what may facilitate the act of slaughtering ones yearning and renouncing the love of praise and commendation?
I would reply: as for slaughtering your yearning then this is made easy by you having certain knowledge that there is nothing that one would desire except that its treasures are in the Hand of Allaah alone and none has power over it save Him. There is no one who may bestow these things to a servant except for Allaah.
As for renouncing the love of praise and commendation then this is made easy by your knowing that there is no one who can praise you such that it would benefit you, or censure and vilify you such that it would harm you save Allaah alone. This is what occurs in the hadeeth in which the Arab said to the Prophet (sallallaahu ’alayhi wa sallam), “my being praised is adornment and my being vilified is disgrace,” to which the Prophet (sallallaahu ’alayhi wa sallam) said, “that is (for) Allaah.” [Reported by at-Tirmidhee [no. 3266] with a saheeh isnaad from Baraa`a bin Aazib (RA).]
So renounce the praise of one whose praise cannot beautify you and the vilification of one whose censure cannot disgrace you! Instead desire the praise of the One whose commendation contains perfect beauty and the One whose censure contains total disgrace.
This cannot be attained except after patience and certainty for when there is no patience and certainty then you are like one who wished to traverse an ocean without a vessel to carry him!
“Be patient! Indeed the Promise of Allaah is true and let not those who are devoid of certainty discourage you from conveying (the message).” [al-Rum (30):60]
“We have made from amongst them leaders, guiding under Our Command when they were patient and believed in Our Signs with certainty.” [al-Sajdah (32):24]