Is it permissible to say that a particular person is one of the awliya’ (close friends) of Allah?
Question

Is it permissible to say that a particular person is a wali or close friend of Allah because of his righteousness and piety, whether he is living or dead, such as saying for example, The scholar so and so is one of the awliya’ of Allah?.
Praise be to Allah.Allah has mentioned the signs by which His close friends or awliya’ may be known. They are: faith (eemaan) and piety (taqwa). Allah says (interpretation of the meaning): 
“No doubt! Verily, the Awliyaa’ of Allah, no fear shall come upon them nor shall they grieve.
Those who believed, and used to fear Allah much (by abstaining from evil deeds and sins and by doing righteous deeds)” [Yoonus 10:62-63]
But it is not possible to be certain that a particular individual is one of the awliya’ of Allah, because achieving true faith and piety are matters of the heart that are hidden, and people cannot find out about them. Hence it is possible to think that someone is likely to be a wali, but it is impossible to be certain. 
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 
All Muslims should measure the deeds of those who are claimed to be awliya’ by that which is in the Qur’aan and Sunnah. If they are in accordance with the Qur’aan and Sunnah, then we hope that he is one of the awliya’ or close friends of Allah, but if they go against the Qur’aan and Sunnah, then he is not one of the awliya’ of Allah. Allah has mentioned in His Book the fair standards by which His awliya’ may be known, as He says (interpretation of the meaning): 
“No doubt! Verily, the Awliyaa’ of Allah, no fear shall come upon them nor shall they grieve.
Those who believed, and used to fear Allah much (by abstaining from evil deeds and sins and by doing righteous deeds)” [Yoonus 10:62-63]
Whoever is a believer and is pious is a close friend of Allah, and whoever is not like that is not a close friend of Allah. If he has some faith and piety then he is a friend of Allah to some extent.  
Nevertheless we cannot be certain about a specific person, but we say in general that everyone who believes and is pious is a friend of Allah (wali)."(Fatawa Muhimmah, p. 83, 84)
And Allah knows best.