There are several planes upon which the intellect functions. We can say that there are many different levels. But higher truths can be experienced by only those individuals who have a high intellectual horizon. Those with a lower intellectual horizon cannot be acquainted with higher realities. The same is true of faith
This is illustrated by the interactions of some of the companions of the Prophet, Umar ibn al-Khattab (d. 23 AH), Maaz ibn Jabal (d. 18 AH), and Abdullah ibn Rawaha al-Ansari (d. 8 AH). As recorded in the books of Hadith these men used to have conversations about God with one another and they would say that they were doing so in order to increase their faith. Once Abdullah ibn Rawaha asked a companion to come and have faith for a moment. The companion who was with him became angry. He said: “Are we not believers?” Then in anger, the companion went to the Prophet and said: “O Messenger of God, have not you seen how Abdullah ibn Rawaha wants to believe for a moment even after we have believed in you?” The Prophet replied: “May God have mercy on Ibn Rawaha, he likes such meetings as even angels envy.” (Musnad Ahmad, Hadith No. 13796)
Faith in God (iman billah) or the initial stage of faith in God is attained after the recitation of the words of the kalimah. But iman is something which goes on growing. Therefore the Quran has likened iman or faith to a plant which keeps growing. “Do you not see how God compares a good word to a good tree? Its root is firm and its branches are in the sky, it yields its fruit each season with its Lord’s permission.” (The Quran, 14:24-25) When a believer thinks about God, when he studies this subject, when he observes the universe from this angle, throughout his contemplation, his faith in God keeps on increasing, he continues to discover God’s high attributes and he keeps gaining in conviction again and again. Such are the believers who undergo the experience of iman billah (faith in God) on a higher intellectual plane.
Source: Discovering God