Whenever the Prophet ﷺ intended to proceed on a journey, he used to draw lots amongst his wives and would take the one upon whom the lot fell. Once, before setting out for Jihad, he drew lots amongst us and the lot came to me; so I went with the Prophet; and that happened after the revelation of the Verse Hijab (i.e. veiling).  

كَانَ النَّبِيُّ ﷺ إِذَا أَرَادَ أَنْ يَخْرُجَ أَقْرَعَ بَيْنَ نِسَائِهِ فَأَيَّتُهُنَّ يَخْرُجُ سَهْمُهَا خَرَجَ بِهَا النَّبِيُّ ﷺ فَأَقْرَعَ بَيْنَنَا فِي غَزْوَةٍ غَزَاهَا فَخَرَجَ فِيهَا سَهْمِي فَخَرَجْتُ مَعَ النَّبِيِّ ﷺ بَعْدَ مَا أُنْزِلَ الْحِجَابُ