Hazrat Moulana Muhammad Ilyaas (rahmatullahi ‘alaih) once mentioned:
Despite the Ambiyaa (‘alaihimus salaam) being sinless and receiving divine protection from Allah Ta‘ala, and despite them being blessed with divine knowledge and guidance directly from Allah Ta‘ala, when they interacted with all types of people for the purpose of propagating deen to them, the impurity of people’s hearts would affect their illuminated hearts.
The Ambiyaa (‘alaihimus salaam) would cleanse their illuminated hearts of the ill-effects (of the association of people) through them remaining in seclusion and engaging in zikrullah and ibaadah.
In Surah Muzzammil, when commanding Rasulullah (sallallahu ‘alaihi wasallam) to perform Tahajjud Salaah, Allah Ta‘ala mentioned:
اِنَّ لَكَ فِی النَّهارِ سَبۡحًا طَوِیۡلًا ﴿۷﴾
Indeed, during the day, you have a prolonged occupation (through guiding the ummah in matters of deen). (Surah Muzzammil v. 7)
In this verse, there is also an indication that there was a need for Rasulullah (sallallahu ‘alaihi wasallam) to remain in seclusion during the night to engage in ibaadah on account of him interacting with people during the day.
Thereafter, in the very next verse, Allah Ta‘ala says:
وَ اذۡکُرِ اسۡمَ رَبِّكَ وَتَبتلۡ اِلَیۡه تَبۡتِیۡلًا ﴿۸﴾
And remember the name of your Rabb (i.e. engage in the zikr of Allah), and devote yourself to Him with exclusive devotion. (Surah Muzzammil v. 8)
This verse further supports and substantiates the point that there is a special need for those people who engage in the activities of tableegh to engage in zikrullah, having fikr (concern for their islaah), and performing ibaadah in seclusion. We, who are in tableegh, should also practise upon this verse (by performing tahajjud and remembering Allah Ta‘ala in seclusion during the night).
In fact, our need to do this is even greater, as firstly, we are weak and our hearts are filled with darkness. Then secondly, those seniors from whom we acquire deeni benefit and guidance are also not sinless, and thirdly, the people whom we interact with for the purpose of tableegh are the normal laymen (who are also not sinless).
In essence, we ourselves are filled with human weaknesses, and on both sides, we are surrounded by people who are also filled with human weaknesses, and this will certainly have an effect upon our hearts. Therefore, it is vitally important for us to engage in zikrullah and the ibaadah of Allah Ta‘ala in seclusion during some part of the night.
This is the special remedy and treatment for the evil effects that can come onto one’s heart when associating with people.
(Malfoozaat Hazrat Moulana Muhammad Ilyaas (rahmatullahi ‘alaih) pg. 71-72)