Bukhari

Hadith Commentary:
The objective of migration (hijrah) that existed during the era of the Messenger (sallallahu alayhi wa sallam) came to an end with the conquest of Makkah, because the entire Arabian Peninsula became the abode of Islam (dar al-Islam). In later times, however, whenever circumstances resembling the Makkan period arise, the process of migration continues. Likewise, Islam and jihad also remain. Therefore, allegiance (bay‘ah) can be taken for all of these. By bay‘ah is meant an oath and affirmation that one will certainly remain steadfast upon it and will never go against it. There are many types of bay‘ah, which will be explained.

Hadith Commentary:
1.
According to the first hadith, the noble Companions (radi Allahu anhum) pledged allegiance (bay‘ah) to the Messenger of Allah (sallallahu alayhi wa sallam) at the occasion of the Battle of the Trench (Ghazwah Khandaq) that they would continue to perform jihad as long as they lived.
The meaning of this pledge was that they would not flee from the battlefield, even if their lives were lost in this path.
In the second hadith, there is mention of taking the pledge from Hazrat Mujashi‘ (radi Allahu anhu).
He had accepted Islam at the time of the Conquest of Makkah.
At that time, there was no opportunity to migrate (hijrah) from Makkah, because Makkah had now become a land of Islam (dar al-salam).
2.
The Messenger of Allah (sallallahu alayhi wa sallam) used to take the pledge for migration (hijrah) from those who accepted Islam before the Conquest of Makkah; from those who accepted Islam after that, the pledge for migration was not taken, rather, the pledge for jihad was taken from them, because jihad is obligatory (fard) until the Day of Judgment. However, if a person’s faith is in danger in a certain country, then it is necessary to migrate from there to a place where faith is secure and there is no obstacle in acting upon its requirements.
And Allah knows best.

Hadith Commentary: Benefits and Issues: The migration (hijrah) in which there was virtue, and which was intended and obligatory, was to leave one’s homeland and settle in Madinah, so that the strength of the Muslims could be gathered in one place and dominance could be achieved over the polytheists of Makkah. Now, when Makkah has become a land of peace (dar al-salam), migrating to Madinah is no longer a cause of distinction and honor, because Makkah has been conquered and Islam has attained dominance, strength, and glory. Therefore, the honor and distinction of this migration has already been attained by the Muhajirun (migrants). Thus, if now someone lives in a place where it is not possible to manifest the religion and fulfill its obligations and duties, and he is able to migrate, then he should migrate. However, if there is no restriction on manifesting Islam and fulfilling its obligations and duties, or if migration is not possible, then migration is not obligatory for him.