What is the context of revelation for this āyah?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. Jundub ibn ʿAbd Allāh reported: "The Messenger of Allah (ﷺ) sent a group of people and appointed Abū ʿUbaydah as their leader. However, as he was leaving, Abū ʿUbaydah became very emotional about departing from the Messenger of Allah (ﷺ), so the Prophet appointed ʿAbdullāh ibn Jahsh in his place. The Prophet wrote him a letter and instructed him not to read it until he reached a certain location. He also said, 'Do not force anyone from your companions to go with you.' When they reached the designated location, ʿAbdullāh read the letter, said 'To God and His Messenger, we listen and obey,' and shared the contents with his companions. Two of them chose to return, while the rest continued and attacked Ibn al-Ḥaḍramī, killing him. They were unsure whether that day was in Rajab or Jumādā al-Ākhirah. The polytheists said to the Muslims: 'You have killed during the sacred month!' The Muslims came to the Prophet (ﷺ) and informed him of what happened, and this verse was revealed. Some Muslims said: 'If they have done good, then what reward do they have?' Then the verse was revealed: "Indeed, those who have believed and those who have emigrated..." to "Most Merciful" (Al-Baqarah: 218)." Al-Zuhrī said: "Ibn al-Ḥaḍramī's name was ʿAmr, and the one who killed him was ʿAbdullāh ibn Wāqid al-Laythī." Ibn ʿAbbās stated that the Prophet's Companions (ﷺ) thought that night was in Jumādā, but it turned out to be the beginning of Rajab.

1. The Prophet (ﷺ) entered Makkah during a sacred month on the Day of the Conquest when the polytheists criticized him for fighting in a sacred month.