Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: A man accepted Islam. When the Prophet (peace and blessings be upon him) migrated, his family feared that he would follow the Prophet (peace and blessings be upon him), so they tied him up. He wrote to the Prophet (peace and blessings be upon him): You know of my Islam, so have me brought to you or get me released. So the Prophet (peace and blessings be upon him) sent six men on a camel and said: Perhaps you will find someone in a house who will help you concerning him. Then the Prophet (peace and blessings be upon him) declared him free.
Al-Bazzar recorded it, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العتق / 7245