Sahih Bukhari Volume 2, Book 25, Hadith 1603

حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، حَدَّثَنَا حَمَّادٌ ـ هُوَ ابْنُ زَيْدٍ ـ عَنْ أَيُّوبَ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ قَدِمَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَصْحَابُهُ فَقَالَ الْمُشْرِكُونَ إِنَّهُ يَقْدَمُ عَلَيْكُمْ، وَقَدْ وَهَنَهُمْ حُمَّى يَثْرِبَ‏.‏ فَأَمَرَهُمُ النَّبِيُّ صلى الله عليه وسلم أَنْ يَرْمُلُوا الأَشْوَاطَ الثَّلاَثَةَ، وَأَنْ يَمْشُوا مَا بَيْنَ الرُّكْنَيْنِ، وَلَمْ يَمْنَعْهُ أَنْ يَأْمُرَهُمْ أَنْ يَرْمُلُوا الأَشْوَاطَ كُلَّهَا إِلاَّ الإِبْقَاءُ عَلَيْهِمْ‏

Narrated By Ibn Abbas : When Allah's Apostle and his companions came to Mecca, the pagans circulated the news that a group of people were coming to them and they had been weakened by the Fever of Yathrib (Medina). So the Prophet ordered his companions to do Ramal in the first three rounds of Tawaf of the Ka'ba and to walk between the two corners (The Black Stone and Yemenite corner). The Prophet did not order them to do Ramal in all the rounds of Tawaf out of pity for them.