Ata bin Abi Rabah (may Allah have mercy on him) and Mujahid (may Allah have mercy on him) said in the explanation of Allah the Exalted’s statement: ﴿an enemy to you while he is a believer﴾: It refers to a person who is from an enemy people, then he accepts Islam and wishes to come to the Muslims, but is mistakenly killed on the way. In this case, there is no blood money (diyah) for him, but it is obligatory upon the killer to free a believing slave.
Hadith Referenceسنن سعید بن منصور / كتاب التفسير / 665
Hadith Gradingمحدثین:سنده فيه إسماعيل بن عياش وهو مدلِّس ولم يصرِّح هنا بالسماع، وهو حسن الحديث إذا روى عن الشاميين، وأما إذا روى عن غيرهم فحديثه ضعيف
Hadith Takhrij«أخرجه سعيد بن منصور فى (سننه) برقم: 665، 2827»