It is permissible to point to a non-Muslim with the hand and tell him “You are a non-Muslim” while one really knows that he is a non-Muslim, is this permissible taking into account that whoever does not declare a non-Muslim a Kaafir or doubt in their belief then he is a non-Muslim himself as mentioned by the reviver of the Sunnah, Muhammad Abdal Wahaab, and Ibn Baaz, may Allaah have mercy on them. Is it permissible to do so or not?

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 is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

There is no doubt that whoever does not declare a non-Muslim as a non-Muslim or doubts his disbelief is a disbeliever himself. This is a solid principle in Islam. But this does not mean (as the questioner mentioned) that he would utter this to the non-Muslim, rather it is not wise to do so. How could this be said to a person whom we, Muslims, hope to soften his heart to embrace Islam especially if he believes that he is on the truth? So telling him these words would repel him from listening or accepting the truth, unless there is really a religious need for it. This could only be said to an arrogant and stubborn person.

Allaah Knows best.