Then said Philip: 'Great is the mercy of God upon whoso loveth him. Tell us O master, how Abraham came to the knowledge of God.'
          Jesus answered: 'Having arrived nigh unto the house of his father, Abraham feared to go into the house; so he removed some distance from the house and sat under a palm tree, where thus abiding by himself he said: "It needs must be that there is a God who hath life and power more than man, since he maketh man, and man without God could not make man. Thereupon, looking round upon the stars, the moon, and the sun, he thought that they had been God. But after considering their variableness with their movements, he said: "It needs must be that God move not, and that clouds hide him not; otherwise men would be brought to naught." Whereupon, remaining thus in suspense, he heard himself called by name,    "Abraham!" And so, turning round and not seeing any one on any side, he said: "I have surely heard myself called by name, 'Abraham.' " Thereupon, two other times in like manner. he heard himself called by name, "Abraham!"
          'He answered: "What calleth me?"
          'Then he heard it said: "I am the angel of God, Gabriel."
          'Therefore was Abraham filled with fear; but the angel comforted him, saying: "Fear not, Abraham, for that thou art friend of God; wherefore, when thou didst break in pieces the gods of men, thou wert chosen of the God of the angels and prophets; insomuch that thou art written in the book of life."
           'Then said Abraham: "What ought I to do, to serve the God of the angels and holy prophets?"
           'The angel answered: "Go to that fount and wash thee, for God willeth to speak with thee."
            'Abraham answered: "Now, how ought I to wash me?"
            'Then the angel presented himself unto him as a beautiful youth, and washed himself in the fount, saying: "Do thou in turn likewise to thyself, O Abraham." When Abraham had washed himself, the angel said: "Go up that mountain, for God willeth to speak to thee there."
              'He ascended the mountain as the angel said to Abraham, and having sat down upon his knees he said to himself: "When will the God of the angels speak to me?"
              'He heard himself called with a gentle voice: "Abraham!"
              'Abraham answered him: "Who calleth me?"
              'The voice answered: "I am thy God, O Abraham."
              'Abraham, filled with fear, bent his face to earth, saying: "How shall thy servant hearken unto thee, who is dust and ashes!"
              'Then said God: "Fear not, but rise up, for I have chosen thee for my servant, and I will to bless thee and make thee increase into a great people. Therefore go thou forth from the house of thy father and of thy kindred, and come to dwell in the land which I will give to thee and to thy seed."
              'Abraham answered: "All will I do, Lord; but guard me that none other god may do me hurt."
              'Then spake God, saying: "I am God alone. and there is none other God but me. I strike down, and make whole; I slay, and give life; I lead down to hell, and I bring out thereof, and none is able to deliver himself out of my hands." Then God gave him the covenant of circumcision; and so our father  Abraham knew God.'
             And having said this, Jesus lifted up his hands, saying: 'To thee be honour and glory, O God. So be it!'

  An Islamic Perspective and Commentary
Ishaq Zahid

Abraham's search for the true God is narrated in the Quran as follows:

006.074 Lo! Abraham said to his father Azar: "Takest thou idols for gods? For I see thee and thy people in manifest error." 006.075 So also did We show Abraham the power and the laws of the heavens and the earth, that he might (with understanding) have certitude. 006.076 When the night covered him over, He saw a star: He said: "This is my Lord." But when it set, He said: "I love not those that set." 006.077 When he saw the moon rising in splendour, he said: "This is my Lord." But when the moon set, He said: "unless my Lord guide me, I shall surely be among those who go astray." 006.078 When he saw the sun rising in splendour, he said: "This is my Lord; this is the greatest (of all)." But when the sun set, he said: "O my people! I am indeed free from your (guilt) of giving partners to God. 006.079 "For me, I have set my face, firmly and truly, towards Him Who created the heavens and the earth, and never shall I give partners to God." 006.080 His people disputed with him. He said: "(Come) ye to dispute with me, about God, when He (Himself) hath guided me? I fear not (the beings) ye associate with God: Unless my Lord willeth, (nothing can happen). My Lord comprehendeth in His knowledge all things. Will ye not (yourselves) be admonished? 006.081 "How should I fear (the beings) ye associate with God, when ye fear not to give partners to God without any warrant having been given to you? Which of (us) two parties hath more right to security? (tell me) if ye know. 006.082 "It is those who believe and confuse not their beliefs with wrong - that are (truly) in security, for they are on (right) guidance." 006.083 That was the reasoning about Us, which We gave to Abraham (to use) against his people: We raise whom We will, degree after degree: for thy Lord is full of wisdom and knowledge.

It is also worth noting that Abraham (peace be on him) was instructed by angel Gabriel to wash himself and when he heard God speak, he prostrated. Ablution and prostrations are mandated rituals in Islam performed five times daily by Muslims all over the world.