Abu Hurairah reported,

When he was on his way intending to embrace Islam, accompanied by his servant boy, the two became separated from each other. He arrived later while Abu Hurairah was sitting with the Prophet ﷺ, and the Prophet ﷺ said, "Abu Hurairah, here is your servant boy who has come to you."He replied, "I call you to witness that he is free."He said this as he was reciting, "What a long and exhausting night, yet it brought deliverance from the abode of disbelief."

عن أبي هريرة

أنه لما أقبل يريد الإسلام، ومعه غلامه ضل كل واحد منهما من صاحبه، فأقبل بعد ذلك، وأبو هريرة جالس مع النبي ﷺ، فقال النبي ﷺ: يا أبا هريرة، هذا غلامك قد أتاك. فقال: أما إني أشهدك أنه حر، قال فهو حين يقول: يا ليلة من طولها وعنائها على أنها من دارة الكفر نجت.