After every farz salath does our beloved Prophet Muhammad SAW, any time, loudly recited "Haq La Ilaha Illallah"? If any one loudly recites "Haq La Ilaha Illallah" after every farz salath, is it a right practice?
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
We do not know of any evidence from the Sunnah that the Prophet, sallallaahu ‘alayhi wa sallam, used to say, ‘Haqq La Ilaaha Illa Allaah,’ aloud after the obligatory Salah. There are some reported Thikr formulas that the Prophet, sallallaahu ‘alayhi wa sallam, used to recite after Salah as we explained in Fatwa 81736. However, the named Thikr (Haqq ...) is not one of them.
It has also been reported that in the lifetime of the Prophet, sallallaahu ‘alayhi wa sallam, it was the custom to recite the Athkaar aloud after Salah. Some scholars stated that the Athkaar were recited aloud at first in order to teach (the Companions) the Athkaar and then they used to recite them silently. Therefore, the Sunnah is to recite the Athkaar silently, not loudly, after Salah. Please refer to Fatwa 83390.
Allaah Knows best.