To Purify The Heart

Hadrat Imam-i Rabbani [1] says in the 17th letter of the third volume of his Maktubat:

After correcting our belief and doing the worships compatible with the Shari'at [2] , we should enrich our time with dhikr-i ilahi (mentioning Allah's name); we should not live one moment without remembering Allahu ta'ala. While the body, the hands and feet are busy with worldly affairs, the heart should always be with Him, getting flavour from remembering Him. This great fortune falls to anybody's lot in a short time who is on the way shown by our superiors.

Alhamdulillah [3] , you know that this is so. Perhaps, some of it has occurred to you, even though it may be very little. You should not let go of what you have obtained; you should thank Allah very much and strive so that it may increase. Things which everybody may attain only in the end are attained at the beginning of this way. Then, even when they obtained little, they have still obtained very much. For they know of the end, yet at the beginning. Nevertheless, you should not be contented with what you have obtained no matter how much it is. You should not, however, discontinue thanking Allahu ta'ala. You should both thank and wish that it will increase. The purpose of the heart's mentioning Him is to dispel the love of anybody else besides Him from the heart. The illness of the heart is that it has various attachments. Unless such attachments are eradicated, real iman [4] will not fall to one's lot. It will not be easy to carry out the commandments and the prohibitions of the Shari'at.

[1] Hadrat: title of respect used before the names of great people like and Islamic scholars.
[2] Shari'at: (pl. of Shari'a) i) rules and commandments as a whole of the religion. ii) religion.
[3] hamd: glory, glorification; gratitude and praise. : thanksgiving
[4] iman: faith, belief, beliefs of Islam; kalam, i'tiqad.