Narrated Aisha, Ummul Mu'minin: while she was on a journey along with the Messenger of Allah (ﷺ): I had a race with him (the Prophet) and I outstripped him on my feet. When I became fleshy, (again) I had a race with him (the Prophet) and he outstripped me. He said: This is for that outstripping.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو صَالِحٍ الأَنْطَاكِيُّ، مَحْبُوبُ بْنُ مُوسَى أَخْبَرَنَا أَبُو إِسْحَاقَ، - يَعْنِي الْفَزَارِيَّ - عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، وَعَنْ أَبِي سَلَمَةَ، عَنْ عَائِشَةَ، رَضِيَ اللَّهُ عَنْهَا أَنَّهَا كَانَتْ مَعَ النَّبِيِّ صلى الله عليه وسلم فِي سَفَرٍ قَالَتْ فَسَابَقْتُهُ فَسَبَقْتُهُ عَلَى رِجْلَىَّ فَلَمَّا حَمَلْتُ اللَّحْمَ سَابَقْتُهُ فَسَبَقَنِي فَقَالَ " هَذِهِ بِتِلْكَ السَّبْقَةِ " .
sunnah.com