A doubt: Resorting to righteous people for intercession is not part of polytheism

This is forbidden, why? Because I do not know whether he is righteous or not and whether he will be of them or not.

This is forbidden as it is a means to polytheism, but you may say to the righteous person: Invoke Allah for me. This is permissible even if it is reprehensible at some scholars as it is reliance on righteous people instead of righteous deeds. It also affects the perfection of your monotheism, but it is permissible in general since it is meant for benefitting a person as the Prophet (peace be upon him) said to `Umar: "Do not forget us from your invocations, brother."[1] Did the Prophet (peace be upon him) need the invocations of `Umar (may Allah be pleased with him)?

The answer is: Never, but that was for `Umar to benefit from his invocation to the Prophet (peace be upon him) while he is not present, so Allah would assign two angels to say: Amen, and the same to you.[2] This meaning is explained by Sheikh-ul-Islam ibn Taymiyah and other scholars, which is good.He (may Allah bestow mercy on him) said: "When a person says: I do not associate others with Allah in worship, and resorting to righteous people for intercession is not part of polytheism. Say to him: If you admit that Allah prohibited polytheism more than the prohibition of adultery, and you admit that Allah does not forgive it, so what is that thing which Allah has prohibited and does not forgive it? If he does not know, say to him: How come you free yourself of polytheism while you do not know it? How does Allah prohibit that and mention that He shall not forgive it while you do not ask about it or even know it? Do you think that Allah would forbid something without explaining it to us?"

Al Maqasid As-Samiyat fi Kash Ash-Shubuhat.