It was narrated that Jabir bin Zaid said:

"Ibn 'Abbas said:
'The Messenger of Allah ﷺ, Abu Bakr and 'Umar were among the Muhajirin (emigrants), because they forsook (hajaru) the idolators, and
some of the Ansar were Muhajirun because Al-Madinah was a land of shirk, and they came to the Messenger of Allah ﷺ on the Night of Al-'Aqabah."'

أَخْبَرَنَا الْحُسَيْنُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا مُبَشِّرُ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا سُفْيَانُ بْنُ حُسَيْنٍ، عَنْ يَعْلَى بْنِ مُسْلِمٍ، عَنْ جَابِرِ بْنِ زَيْدٍ، قَالَ قَالَ ابْنُ عَبَّاسٍ إِنَّ رَسُولَ اللَّهِ ﷺ وَأَبَا بَكْرٍ وَعُمَرَ كَانُوا مِنَ الْمُهَاجِرِينَ لأَنَّهُمْ هَجَرُوا الْمُشْرِكِينَ وَكَانَ مِنَ الأَنْصَارِ مُهَاجِرُونَ لأَنَّ الْمَدِينَةَ كَانَتْ دَارَ شِرْكٍ فَجَاءُوا إِلَى رَسُولِ اللَّهِ ﷺ لَيْلَةَ الْعَقَبَةِ .