When the offer of ransom was made, Rasulullah (sallallahu ‘alaihi wasallam) said, “So long as my companions, Sa’d and Utbah, do not return, I will not release your captives, as I fear that you may kill them. If you kill my companions, then I will also kill your people (in retaliation).”
A few days later, Hazrat Sa’d (radhiyallahu ‘anhu) and Hazrat Utbah (radhiyallahu ‘anhu) returned safely. Rasulullah (sallallahu ‘alaihi wasallam) then accepted the ransom and released Uthmaan and Hakam. The moment he was released, Uthmaan returned to Makkah Mukarramah where he died a disbeliever, while Hakam bin Kaysaan embraced Islam and stayed in Madinah Munawwarah, until he was later martyred in the expedition of Bir Ma’oonah.
In regard to this incident (of the disbelievers and Jews condemning the Muslims for fighting during the sacred month) Hazrat Abdullah bin Jahsh (radhiyallahu ‘anhu) composed the following verses of poetry:
تَعُدُّوْنَ قَتْلاً فِي الْحَرَامِ عَظِيْمَةً وَأَعْظَمُ مِنْهُ لَوْ يَرٰى الرشدَ رَاشِدُ
صدودُكُمْ عَمَّا يَقُوْلُ مُحَمَّدُ وَكُفْرٌ بِهِ وَاللهُ رَاءٍ وَشَاهِدُ
You people (kuffaar) consider fighting within the sacred month (of Rajab) as a great sin, but worse than that - if only an intelligent person (among you) would reflect, then he would definitely realise the truth - is your stopping people from what Muhammed (sallallahu ‘alaihi wasallam) is inviting people to and your disbelief in him (is worse than fighting in the sacred months), and Allah is All-Seeing and All-Witnessing.
وَإِخْرَاجُكُمْ مِنْ مَسْجِدِ اللهِ أَهْلَهُ كَيْلاَ يُرٰى فِي الْبَيْتِ لِلّٰهِ سَاجِدُ
And you people removing the people of Allah (i.e. the Muslims) from the musjid of Allah Ta‘ala through which there is no one to make sajdah for Allah Ta‘ala by His house (the Ka’bah Shareef, this is far worse than fighting ion the sacred months).
فَإِنَّا وَإِنْ عَيَّرْتُمُوْنَا بِقَتْلِهِ وَأَرْجَفَ بِالْإِسْلَام ِبَاغٍ وَحَاسِدٌ
سَقَيْنَا مِنِ ابْنِ الْحَضْرَمِـيِّ رِمَاحَنَا بِنَخْلَةَ لَمَّا أَوْقَدَ الْحَرْبَ وَاقِدٌ
دَمًا وَابْنِ عَبْدِ اللهِ عُثْمَانَ بَيْنَنَا يُنَاِزِعُهُ غُلٌّ مِنَ الْقَيْدِ عَانِدٌ
If you condemn us for killing him (i.e. killing Amr ibnul Hadrami in the sacred month of Rajab), and there are many people among you who are inciting trouble by saying this against Islam, then know well that our response to you is that we quenched our spears with the blood of Amr ibnul Hadrami at Nakhlah when Waaqid killed him at the time when he commenced the battle. Uthmaan bin Abdillah was a captive amongst us with fetters and chains burdening him down to the ground.
(Extracted from Seeratul Mustafa 2/54-55)