What is the highest degree a believer who is neither a prophet nor a Companion can reach?

There are four levels of perfection: Prophethood, Siddiqiyyah (truthfulness/sainthood), Martyrdom, and Wilayah (sainthood/guardianship). The highest of these is Prophethood and Messengership, followed by Siddiqiyyah, which is the highest rank after Prophethood. Siddiqiyyah is the perfection of faith in what the Messenger brought, encompassing knowledge, affirmation, and adherence to it. Thus, whoever has the most knowledge of what the Messenger brought and the most perfect affirmation of it, possesses the most complete Siddiqiyyah.

Umar and Uthman, may Allah be pleased with them, reached the highest ranks of Siddiqiyyah. They are in the second and third positions after Abu Bakr As-Siddiq, may Allah be pleased with him, the master of the truthful ones. Among the proofs for this is the saying of Ali, may Allah be pleased with him: "The best of this Ummah after its Prophet is Abu Bakr, then Umar." And his supplication for mercy upon Umar. And the saying of Ibn Umar: "We used to choose among people in the time of the Prophet, peace be upon him, and we would choose Abu Bakr, then Umar ibn Al-Khattab, then Uthman ibn Affan, may Allah be pleased with them."

Ibn Al-Qayyim affirmed that Umar ibn Al-Khattab, may Allah be pleased with him, is the head of the truthful ones. The absence of mentioning Siddiqiyyah for Umar and Uthman in some hadiths, such as the hadith (definition) of Amr ibn Murrah Al-Juhani, may Allah be pleased with him, does not negate this quality for them. It can be established by other proofs, such as the verse from Surat Al-Hadid, where Allah included Umar among the truthful ones.