Once a slave of Ibn ʿUmar fled and joined the Byzantine. Khalid bin Al-Walid got him back and returned him to ʿAbdullah (bin ʿUmar). Once a horse of Ibn ʿUmar also ran away and followed the Byzantines, and he (i.e. Khalid) got it back and returned it to ʿAbdullah.
وَأَنَّ فَرَسًا لاِبْنِ عُمَرَ عَارَ فَلَحِقَ بِالرُّومِ فَظَهَرَ عَلَيْهِ فَرَدُّوهُ عَلَى عَبْدِ اللَّهِ قَالَ أَبُو عَبْد اللَّهِ عَارَ مُشْتَقٌّ مِنْ الْعَيْرِ وَهُوَ حِمَارُ وَحْشٍ أَيْ هَرَبَ