Imam al-Shafi'i (may Allah have mercy on him) said: "It is narrated from Imam al-Awza'i (may Allah have mercy on him): 'If he does not give them the wealth, he should return to their captivity.'"
He (further) said: "Whoever adopts the position of Imam al-Awza'i (may Allah have mercy on him), and whoever holds his view, in my opinion argues only from what is narrated from some of them: that the Prophet (peace and blessings be upon him) made peace with the people of Hudaybiyah on the condition that whoever of them came to him as a Muslim after the treaty, he would return him. So Sayyiduna Abu Jandal (may Allah be pleased with him) came to him (peace and blessings be upon him), and he (peace and blessings be upon him) returned him to his father; and Sayyiduna Abu Basir (may Allah be pleased with him) came, and he (peace and blessings be upon him) returned him (too). Then Abu Basir killed the man with whom he had been sent back, then came to the Prophet (peace and blessings be upon him) and said: 'I have fulfilled (the covenant) with them, and Allah has saved me from them.' The Prophet (peace and blessings be upon him) did not send him back, nor did he reproach him for it; rather, he left him as he was. So he stayed on the road to Syria, attacking every (trade caravan of) wealth belonging to Quraysh, until Quraysh, because of the harm that reached them from him, requested the Messenger of Allah (peace and blessings be upon him) to take him to himself (peace and blessings be upon him)."
Imam al-Shafi'i (may Allah have mercy on him) said: "This hadith has been narrated in this way, as I have described it, by some of the people of the Maghazi (the biographers of the campaigns), and I do not recall its chain at present."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / Q18427