حَدَّثَنَا مُحَمَّدُ بْنُ الْعَلاَءِ، وَعُثْمَانُ بْنُ أَبِي شَيْبَةَ، - الْمَعْنَى وَاحِدٌ - قَالاَ حَدَّثَنَا حَفْصٌ، عَنْ عَاصِمٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَقَامَ سَبْعَ عَشْرَةَ بِمَكَّةَ يَقْصُرُ الصَّلاَةَ ‏.‏ قَالَ ابْنُ عَبَّاسٍ وَمَنْ أَقَامَ سَبْعَ عَشْرَةَ قَصَرَ وَمَنْ أَقَامَ أَكْثَرَ أَتَمَّ ‏.‏ قَالَ أَبُو دَاوُدَ قَالَ عَبَّادُ بْنُ مَنْصُورٍ عَنْ عِكْرِمَةَ عَنِ ابْنِ عَبَّاسٍ قَالَ أَقَامَ تِسْعَ عَشْرَةَ ‏.‏

Narrated Abdullah ibn Abbas: The Messenger of Allah (PBUH) had a stop of seventeen days in Mecca and he shortened the prayer (i.e. prayed two rak'ahs at each time of prayer). Ibn Abbas said: He who stays seventeen days should shorten the prayer; and who stays more than that should offer complete prayer. Abu Dawud said: The other version transmitted by Ibn 'Abbas through a different chain adds: He (the Prophet) had a stop of nineteen days (in Mecca). Translation Not Available

Book Ref: Sunan Abi Dawud Book 4 Hadith 1230
Web Ref:  Sunan Abi Dawud Book 4 Hadith 1226