Sahih Muslim 1269
Sahih Muslim · Book 15: The Book of Pilgrimage · It is recommended to touch the two Yemeni Corners in Tawaf and not the other two corners
وَحَدَّثَنِي أَبُو الطَّاهِرِ ، أَخْبَرَنَا ابْنُ وَهْبٍ ، أَخْبَرَنَا عَمْرُو بْنُ الْحَارِثِ ، أَنَّ قَتَادَةَ بْنَ، دِعَامَةَ حَدَّثَهُ أَنَّ أَبَا الطُّفَيْلِ الْبَكْرِيَّ حَدَّثَهُ أَنَّهُ، سَمِعَ ابْنَ عَبَّاسٍ ، يَقُولُ لَمْ أَرَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَسْتَلِمُ غَيْرَ الرُّكْنَيْنِ الْيَمَانِيَيْنِ .
Ibn 'Abbas (Allah be pleased with them) is reported to have said that he did not see Allah's Messenger (ﷺ) touching other than the Yamani corners.