It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that some men of the Ansar sought permission from the Messenger of Allah (peace and blessings be upon him), saying: "O Messenger of Allah (peace and blessings be upon him)! Give us permission to waive the ransom of our sister's son, Abbas (may Allah be pleased with him)." He (peace and blessings be upon him) said: "By Allah! Do not leave even a single dirham." Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) was a child at that time, but his mother had become Muslim, so Abdullah too became Muslim through his mother's Islam.
Imam al-Bukhari (may Allah have mercy on him) said: Sayyiduna Ibn Abbas (may Allah be pleased with them both) was, with his mother, among the oppressed weak ones, and he was not with his father upon the religion of his people.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12150