This man is Abraham/Ibrahim (peace be upon him), a Prophet of Allâh, and the father of the prophets.
Abraham (peace be upon him), started meditating on the creation of Allâh - Who he still did not know - but he realized His Power and Creativity. He began his journey searching for God, and this is his story as it was narrated by the Holy Qur'an:
75. Thus did we show Ibrâhîm (Abraham) the kingdom of the heavens and the earth for him to be one of those who know (have Faith) with certainty
76. When the night covered him over with darkness he saw a star. He said: "This is my lord." But when it set, he said: "I like not those that set."
77. When he saw the moon rising up, he said: "This is my lord." But when it set, he said: "Unless my Lord guides me, I shall surely be among the people who went astray."
78. When he saw the sun rising up, he said: "This is my lord. This is greater." But when it set, he said: "O my people! I am indeed free from all that you join as partners (in worship, with Allâh).
79. Verily, I have turned my face towards Him Who has created the heavens and the earth, as Hanîfa (Islâmic Monotheism, i.e. worshipping none but Al-lâh Alone), and I am not of Al-Mushrikûn (the ones that associates partners with Allâh, in worship)".
80. His people disputed with him. He said: "Do you dispute with me concerning Allâh while He has guided me? I fear not those whom you associate with Him (Allâh) in worship. (Nothing can happen to me) except when my Lord (Allâh) wills something. My Lord comprehends in His Knowledge all things. Will you not then remember?Holy Qur'an, Sura Al- Anaam (the Herds): 75-80.
Therefore, Abraham (peace be upon him) understood that there is a mighty that has created everything, even the heavens and the Earth, and he felt that these gods worshipped by his people do not protected them from hunger or poverty, and they were far from creating anything, and then it turned out they could not even defend themselves!
Abraham took upon himself the task of seeking the Lord. First, he began looking to the sky and saw a big star, he said: 'this is my Lord', but the star set and disappeared with the falling of the night. Abraham was surprised, how do we take a God which goes away with the falling of the night? … Abraham continued his research until he saw the Moon in the sky, he thought that it was the God he was looking for, but neither the moon lived longer than the star, as it was also gone with the dawn.
When the Prophet Abraham (peace be upon him) saw the Sun, his hope grew, he thought, 'this must be the God I was looking for, this is bigger!' …but not everything that we hope comes true, when the Sun set at the end of the day, the hope of Abraham also dispelled. He suffered frustration and despair, until that God that he was looking for guided him to the true faith, and sent his revelation to inform him that God had chosen him to be the warner of his people and a Prophet.
This is the God whom Abraham (peace be upon him) was looking for; it was not the Sun, the Moon, or the idols worshiped by his people, but Allâh, the One God, the Creator of heaven and Earth.
This journey searching for Allâh, was not the only one, there are other trips made by other persons looking for Allâh, but thousands of years after the death of Abraham (peace be upon him)... article taken from http://knowingallah.com/index.php/en/articles/article/699