Shaykh Ibn Taymiyyah, advising his student, Hafidh Ibn al- Qayyim, to adhere to a specific Dhikr.

Those who have an issue with a shaykh prescribing his students with specific litanies should take heed from the following excerpt from the book on Tasawwuf, written by Hafidh Ibn al- Qayyim:

Hafidh Ibn Qayyim has mentioned in his Madarij as- Salikeen (1: 446) that his teacher, Ahmad Ibn Taymiyyah, said to him one day that the two names of Allāh, الحي and القيوم, have a great effect on the heart, and he also indicated that they were from the al- Ism al- A'zam [greatest names of Allāh]. Hafidh Ibn Taymiyyah said that whosoever constantly recites the words 'يَا حَيُّ يَا قَيُّومُ، لَا إِلَهَ إِلَّا أَنْتَ، بِرَحْمَتِكَ أَسْتَغِيثُ' forty times daily,  between the Sunnah of Fajr and the obligatory prayer, his heart will attain life and, hence, it will not die.

‎وَكَانَ شَيْخُ الْإِسْلَامِ ابْنُ تَيْمِيَّةَ قَدَّسَ اللَّهُ رُوحَهُ شَدِيدَ اللَّهْجِ بِهَا جِدًّا، وَقَالَ لِي يَوْمًا: لِهَذَيْنِ الِاسْمَيْنِ وَهُمَا الْحَيُّ الْقَيُّومُ تَأْثِيرٌ عَظِيمٌ فِي حَيَاةِ الْقَلْبِ، وَكَانَ يُشِيرُ إِلَى أَنَّهُمَا الِاسْمُ الْأَعْظَمُ، وَسَمِعْتُهُ يَقُولُ: مَنْ وَاظَبَ عَلَى أَرْبَعِينَ مَرَّةً كُلَّ يَوْمٍ بَيْنَ سُنَّةِ الْفَجْرِ وَصَلَاةِ الْفَجْرِ يَا حَيُّ يَا قَيُّومُ، لَا إِلَهَ إِلَّا أَنْتَ، بِرَحْمَتِكَ أَسْتَغِيثُ حَصَلَتْ لَهُ حَيَاةُ الْقَلْبِ، وَلَمْ يَمُتْ قَلْبُهُ.

P.S. The above specific prescribed dhikr is not established from the Prophet ﷺ, nor the pious Salaf.