Q:
Has it been reported regarding the mark
on the forehead which is caused by Sujud that it is a mark of the righteous?
A: This
is not a mark of the righteous; the mark of the righteous is only the light which
is seen in the face, the expansion of the heart, good character and such like.
As for the mark on the face which is cause by Sujud, it might be seen on the
faces of those who only offer the obligatory prayers due to the delicateness of
their skin, and it might not be seen in the face of one who prays much and
lengthens his Sujud.
~
Source: Fatawa Arkanul-Islam, Volume 2, page. 480-481,
Shaykh Muhammad bin Salih Al-‘Uthaimeen.