Assalamu alikum many of the kuffar have written book against our Prophet peace be upon him like ALI SINA. He claimed that the persecution of Muslims in Makkah is a myth. Plus please provide me the authenticity of this story and main source. Ibn Katheer mentioned as Bilal did when they were inflicting all sorts of torture on him, even placing a huge rock on his chest in the intense heat and telling him to admit others as partners with Allah. He refused, saying, "Alone, Alone.'' And he said, "By Allah, if I knew any word more annoying to you than this, I would say it.'' May Allah be pleased with him. [Tafsir of Surah an-Nahl verse 106]

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, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

First of all, it should be noted that the people who impugn Islam and those who propagate false information about it, and the hypocrites who attack it, do not harm Islam in anything; rather, they only harm themselves; Allaah Says (what means): {And We did not wrong them, but it was they who were the wrongdoers.}[Quran 43:76]

It is also important that the Muslim should believe with certainty in his religion. As regards those who attack Islam, they may not be convinced by any evidence that would be presented to them, even if this evidence were from the Book of Allaah or the Sunnah of the Prophet . This is due to the blindness that has affected their hearts; Allaah Says (what means): {And who is more unjust than one who is reminded of the verses of his Lord but turns away from them and forgets what his hands have put forth? Indeed, We have placed over their hearts coverings, lest they understand it, and in their ears deafness. And if you invite them to guidance — they will never be guided, then — ever.}[Quran 18:57]

As regards the non-Muslims torturing the Muslims in Makkah at the beginning of the Prophet’s mission, then this is something confirmed without any doubt, as it was reported by Tawaatur (i.e. by a group of narrators from a group of narrators, generation after generation and so forth, and they are all trustworthy people and it is absolutely impossible for them to agree on a lie). This was also written in history and biography books and it cannot be denied except by an ignorant or arrogant person. Khabbaab Ibn Al-‘Aratt said: “We complained to the Prophet (of the persecution inflicted on us by the infidels) while he was sitting in the shade of the Ka’bah, leaning over his Burd (i.e. covering sheet). We said to him, "Would you seek help for us? Would you pray to Allaah for us?" He said: "Among the nations before you a (believing) man would be put in a ditch that was dug for him, and a saw would be put over his head and he would be cut into two pieces; yet that (torture) would not make him give up his religion. His body would be combed with iron combs that would remove his flesh from the bones and nerves, yet that would not make him abandon his religion.” [Al-Bukhari]

As regards the story about the torture of Bilaal which you referred to in the question, and him saying: “One, One (i.e. Allaah is One, Allaah is One).”, then this story is confirmed in the Musnad of Imaam Ahmad and others, with a Hasan [good] chain of narrators.

Also, it is reported in the Mustadrak of Al-Haakim that Jaabir narrated that the Prophet passed by ‘Ammaar and his family while they were being tortured and he said to them: “Have glad tiding, family of Ammaar and family of Yaasir, your destination is Paradise.” Al-Haakim, said: “It (This Hadeeth) is Saheeh (sound) according to the condition of Muslim, but neither Al-Bukhari nor Muslim reported it).” Ath-Thahabi corroborated him, and Al-Albaani classified it as Saheeh in "As-Seerah An-Nabawiyyah".

It is this torture which was the cause of the first migration of the Muslims to Abyssinia and then the second migration to Al-Madeenah. In addition to this, Quraysh had plotted to kill the Prophet himself, and that was the cause of his migration (to Madeenah). The story of the attempt of Quraysh to kill him [the Prophet ] was narrated by Imaam Ahmad in his Musnad from Ibn Abbaas . Its chain of narrators was classified as Hasan by Ibn Katheer and Ibn Hajar .

Allaah Knows best.