Mishkat al-Masabih, hadith 2473

وَعَن صفيةَ بنتِ شيبةَ قَالَتْ: أَخْبَرَتْنِي بِنْتُ أَبِي تُجْرَاةَ قَالَتْ: دَخَلْتُ مَعَ نِسْوَةٍ مِنْ قُرَيْشٍ دَارَ آلِ أَبِي حُسَيْنٍ نَنْظُرُ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَهُوَ يَسْعَى بَيْنَ الصَّفَا وَالْمَرْوَةِ فَرَأَيْتُهُ يَسْعَى وَإِنَّ مِئْزَرَهُ لَيَدُورُ مِنْ شِدَّةِ السَّعْيِ وَسَمِعْتُهُ يَقُولُ: «اسْعَوْا فَإِنَّ اللَّهَ كَتَبَ عَلَيْكُمُ السَّعْيَ» . رَوَاهُ فِي شَرْحِ السُّنَّةِ وَرَوَاهُ أَحْمد مَعَ اخْتِلَاف

Safiya daughter of Shaiba said that the daughter of Abu Tujrat told her she had entered the house of the family of Abu Husain along with some women of Quraish and they had watched God’s messenger while he was running between as-Safa and al-Marwa. She saw his lower garment moving round as he ran because of the vigour with which he did it, and she heard him saying, “Run, for God has prescribed running for you." It is transmitted in Sharh as-sunna, and Ahmad transmitted it with some difference.