Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Yes, every newborn is born in a state of purity in which he is ready to accept the belief in Allah and His Oneness which is the fitrah. Then, his parents either teach him according to this fitrah or take him apart from the Right Path via teaching him wrong creeds and beliefs.
Responding to your question, we would like to cite this Fatwa published on: www.islamweb.net,
Allah Almighty created all people and endowed them with the pre-disposition to believe in and to submit to Him alone. There is no new-born child which is not born with the fitrah (natural disposition of faith). Some people stay with their fitrah, and some are misled by the devils among mankind and jinn.
The Prophet (peace and blessings be him) said in a Qudsi Hadith, “Allah Almighty says, ‘I created all My servants hunafa’ (i.e. following the original religion of monotheism), then the devils misled them from their religion and forbade them from what I made lawful for them and commanded them to associate with Me that which I have not sent down any authority for.” (Muslim)
The Prophet (peace and blessings be him) also said, “Every child is born with the fitrah, but his parents make him a Jew, Christian or a Zoroastrian.” (Al-Bukhari and Muslim)
Imam An-Nawawi said, “Allah’s saying ‘I created all My servants hunafa’’ means Muslims. But it was also interpreted that it means they are ‘pure from sins’ and they are “straight (on the Right Path), turning to Allah and accepting guidance’ Then the devils misled them, so they took them away from what they followed and led them to falsehood.”
Interpreting the verse which reads, “So direct your face toward the religion, inclining to truth. [Adhere to] the fitrah of Allah upon which He has created [all] people. No change should there be in the creation of Allah.” (Ar-Rum 30:43)
Ibn Katheer (may Allah have mercy on him) said, “Allah Almighty tells us to set our face and persevere in the religion which Allah has prescribed for us, the worship of Allah alone, the religion of Ibrahim (Abraham), to which Allah has guided us and which He has perfected for us with the utmost perfection. In this manner, we will also adhere to the sound fitrah with which He created His creation. Allah created His creation to know Him and His Oneness and to know that there is no God except Him.”
He also said, “Allah created all of His slaves equal in regard to the natural fitrah, and no one is born without this sound fitrah, and there is no difference among people regarding this.”
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Allah Almighty knows best.