Praise be to Allah.
Ibn Maajah (150) and Ahmad (3822) narrated that ‘Abdullah ibn Mas‘ood said: The first people to declare their Islam publicly were seven: the Messenger of Allah (blessings and peace of Allah be upon him), Abu Bakr, ‘Ammaar and his mother Sumayyah, Suhayb, Bilaal and al-Miqdaad. With regard to the Messenger of Allah, Allah protected him through his paternal uncle Abu Taalib. With regard to Abu Bakr, Allah protected him through his people. As for the rest, the mushrikoon seized them and made them wear coats of chain-mail and exposed them to the intense heat of the sun. There was none of them who did not do what they wanted them to do, except for Bilaal. He did not care what happened to him for the sake of Allah and his people did not care what happened to him. Then they gave him to the children, who took him around in the streets of Makkah whilst he was saying, Ahad, Ahad (One, One).
Classed as saheeh by al-Albaani in Saheeh Ibn Maajah.
As-Sindi (may Allah have mercy on him) said:
The words “He did not care what happened to him for the sake of Allah” mean that he thought little of himself for the sake of Allah.
What is meant that he (may Allah be pleased with him) felt himself to be very insignificant, so he did not care what happened to him for the sake of Allah. It was all the same to him whether they beat him or reviled him or killed him; all of that was of little significance to him for the sake of Allah. So long as he was on the path of Allah and earning His pleasure, he did not care, and he regarded everything, in comparison to the pleasure of Allah, as worthless and of little value, and he thought it was worth offering his soul willingly for the sake of Allah and not withholding it.
Because he was so strongly committed and steadfast, he did not give in to them with regard to anything that they wanted from him, and he kept repeating the word of Tawheed which increased them in their rage and fury towards him, so they increased their torture of him, and that increased him in strength, faith, steadfastness and certainty – may Allah be pleased with him.
The words “and his people did not care what happened to him” mean that he had no value in their eyes and they did not hold him in any esteem, because he was a black slave who disbelieved in their gods and stubbornly opposed them. He had no power or tribe to protect him or defend him, so they tormented him even more and they gave him to the children who started taking him around in the streets of Makkah, to cause further suffering to him and humiliate him publicly, until Allah saved him from them by means of Abu Bakr as-Siddeeq (may Allah be pleased with him), who bought him and manumitted him.
Al-Bukhaari (3574) narrated that Jaabir ibn ‘Abdullah (may Allah be pleased with him) said: ‘Umar used to say: Abu Bakr is our master, and he manumitted our master – meaning Bilaal.
And Allah knows best.