Ibn Abbas (Allah be pleased with him) reported that the Messenger of Allah (ﷺ) went out during the month of Ramadan in the year of Victory (when Mecca was conquered) and was fasting till he reached Kadid (a canal situated at a distance of forty-two miles from Mecca) and he then broke the fast. And it was the habit of the Companions of the Messenger of Allah (ﷺ) to follow him in every new thing (or act). So they followed him also (in this matter).
Source: sunnah.com
Other translations
Arabic
حَدَّثَنِي يَحْيَى بْنُ يَحْيَى، وَمُحَمَّدُ بْنُ رُمْحٍ، قَالاَ أَخْبَرَنَا اللَّيْثُ، ح وَحَدَّثَنَا قُتَيْبَةُ بْنُ، سَعِيدٍ حَدَّثَنَا لَيْثٌ، عَنِ ابْنِ شِهَابٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، عَنِ ابْنِ عَبَّاسٍ، - رضى الله عنهما - أَنَّهُ أَخْبَرَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم خَرَجَ عَامَ الْفَتْحِ فِي رَمَضَانَ فَصَامَ حَتَّى بَلَغَ الْكَدِيدَ ثُمَّ أَفْطَرَ وَكَانَ صَحَابَةُ رَسُولِ اللَّهِ صلى الله عليه وسلم يَتَّبِعُونَ الأَحْدَثَ فَالأَحْدَثَ مِنْ أَمْرِهِ .
sunnah.com