Faith (Iman) is like a tree, the roots of which go into the heart: its trunk is in reason, and its branches are in the instincts, while imagination is its new shoots and leaves - (senses of) the body. The foundation (asl) of faith is love for the Mawla (Imam-e-Zaman). And if this foundation, that is , this love, and the roots of faith are strong and in good condition, all other parts of the tree, such as its trunk, its branches and leaves, can be expected to continue to flourish even if they are (accidentally) damaged. If, on the contrary, the roots are not well grounded, or even rotten, the whole tree will soon dry, and then will become good for nothing except to be used as fuel.
Thus love for the Mawla is everything, being the root of faith. If it is not strong, all the acts of outward piety (a’mal-i zahiri) which are like leaves of the tree, will fade. If you have thousands of leaves, fresh and of good colour, they will dry in a short time, and then a very small fire will be sufficient to burn them completely.
From Risala dar haqiqat-i din by Pir Shihabu’d-Din Shah Al-Husayni, translated as True Meaning of Religion by Wladimir Ivanow.
Pir Shihabu’d-Din Shah Al-Husayni was the eldest son of the 47th Ismaili Imam, Aga Ali Shah, also known as Aga Khan II. His writings represent the earliest examples of a modern revival in Nizari literary activities in Persian. True Meaning of Religion was an incomplete treatise and contains a summary exposition of certain Ismaili teachings with a special reference to the doctine of Imamat as well as ethical and mystical aspects of the Ismaili Tariqah.
Pir Shihabu’d-Din Shah was only 33 when he died due to a chest related illness. His death occured a few months before the demise of his father, Imam Aga Ali Shah, who was succeded to the throne of Imamat by Sir Sultan Mahomed Shah, Aga Khan III, who was then only eight years of age.