All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
  is His slave and Messenger.
Allaah Says (what means): {Abraham was neither a Jew nor a Christian, but he was one inclining toward truth, a Muslim [submitting to Allaah]. And he was not of the polytheists.}  [Quran 3:67]              
In the above verse, Allaah clarifies that Ibraheem [Abraham] 
  was neither a Jew nor a Christian. 
Undoubtedly, Ibraheem 
  came before Moosa [Moses] 
   because the latter was from the descendants of Ya'koob [Jacob], the son of Ishaq, who was the son of Ibraheem, may Allaah exalt their mention.
Indeed Ibraheem, may Allaah exalt their mention, was a Muslim monotheist [believing and submitting himself to Allaah Alone] exactly like all other prophets before him. Allaah Says (what means): {Truly, the religion with Allaah is Islam.} [Quran 3:19]              
Allaah Says about the queen of Sheba (what means): {She said, “My Lord, indeed I have wronged myself, and I submit with Solomon to Allaah, Lord of the worlds.”} [Quran 27:44]           
Moreover, Allaah Says on the tongue of Yoosuf [Josef] 
  (what means): {''Cause me to die a Muslim and join me with the righteous.”} [Quran 12:101]              
Also, Allah says about Ya'koob [Jacob] 
  (what means): {Indeed Allaah has chosen for you this religion, so do not die except while you are Muslims.”} [Quran 2:132].              
Allaah revealed Books and sent Prophets among the descendants of Ibraheem 
  but all of them were sent with his [Ibraheem's] religion; Allaah Says (what means): {Then We revealed to you, [O Muhammad 
], to follow the religion of Abraham inclining toward truth and he was not of those who associate with Allaah.} [Quran 16:123]              
Allaah also Says (what means): {Indeed, the most worthy of Abraham among the people are those who followed him [in submission to Allaah] and this prophet [i.e. Muhammad, sallallaahu ‘'alayhi wa sallam] and those who believe [in his message]. And Allaah is the ally of the believers.} [Quran 3:68]
Allaah Knows best.