Abdullah bin Abbas reported,

He said, "There were some people from the inhabitants of Mecca who had embraced Islam but kept their faith hidden. When the polytheists set out for Badr, they forced these men to go with them, and some of them were killed on the day of Badr while in the ranks of the polytheists.The Muslims said, 'These were our companions, Muslims who were taken out by force,' and they sought forgiveness for them. So this verse was revealed, 'Indeed, those whom the angels take in death while wronging themselves' [Nisa 4:97].The Muslims wrote with this verse to those who remained in Mecca, and they set out. But when they had reached part of the way, the polytheists became aware of them and of their departure, caught up with them, and brought them back, so they returned with them. Then this verse was revealed, 'And among the people is he who says, We believe in Allah, but when he is harmed for the cause of Allah, he considers the trial of the people as the punishment of Allah' [Ankabut 29:10].The Muslims wrote to them about this, and they grieved. Then this verse was revealed, 'Then indeed your Lord, to those who emigrated after they had been compelled and thereafter fought and were patient, indeed your Lord, after that, is Forgiving and Merciful' [Nahl 16:110]. So they wrote to them with this."

عن ابن عباس

قال كان ناس من أهل مكة أسلموا، وكانوا مستخفين بالإسلام، فلما خرج المشركون إلى بدر أخرجوهم مكرهين، فأصيب بعضهم يوم بدر مع المشركين، فقال المسلمون: أصحابنا هؤلاء مسلمون أخرجوهم مكرهين، فاستغفروا لهم. فنزلت هذه الآية: {ان الذين توفىهم الملىكة ظالمي انفسهم} الآية، فكتب المسلمون إلى من بقي منهم بمكة بهذه الآية، فخرجوا حتى إذا كانوا ببعض الطريق ظهر عليهم المشركون وعلى خروجهم، فلحقوهم فردوهم، فرجعوا معهم، فنزلت هذه الآية: {ومن الناس من يقول ءامنا بالله فإذا أوذي في الله جعل فتنة الناس كعذاب الله} [العنكبوت: ١٠] فكتب المسلمون إليهم بذلك فحزنوا، فنزلت هذه الآية {ثم إن ربك للذين هاجروا من بعد ما فتنوا ثم جهدوا وصبروا إن ربك من بعدها لغفور رحيم} [النحل: ١١٠] فكتبوا إليهم بذلك.