Ibn Umar was asked: In which month did the Messenger of Allah perform Umrah? He said: 'During Rajab.' So Aishah said: 'The Messenger of Allah did not perform Umrah except that he was with him - meaning Ibn Umar - and he did not ever perform Umrah in the month of Rajab.'"  

سُئِلَ ابْنُ عُمَرَ فِي أَىِّ شَهْرٍ اعْتَمَرَ رَسُولُ اللَّهِ ﷺ فَقَالَ فِي رَجَبٍ قَالَ فَقَالَتْ عَائِشَةُ مَا اعْتَمَرَ رَسُولُ اللَّهِ ﷺ إِلاَّ وَهُوَ مَعَهُ تَعْنِي ابْنَ عُمَرَ وَمَا اعْتَمَرَ فِي شَهْرِ رَجَبٍ قَطُّ  

"The Prophet performed Umrah four times, one of them was during Rajab."  

أَنَّ النَّبِيَّ ﷺ اعْتَمَرَ أَرْبَعًا إِحْدَاهُنَّ فِي رَجَبٍ