Narrated Abdullah ibn Abbas:

The Messenger of Allah ﷺ 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).

حَدَّثَنَا مُحَمَّدُ بْنُ الْعَلاَءِ، وَعُثْمَانُ بْنُ أَبِي شَيْبَةَ، - الْمَعْنَى وَاحِدٌ - قَالاَ حَدَّثَنَا حَفْصٌ، عَنْ عَاصِمٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ رَسُولَ اللَّهِ ﷺ 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 .