It is recommended to touch the two Yemeni Corners in Tawaf and not the other two corners Sahih Muslim 1267 b
Arabic hadith text
وَحَدَّثَنِي أَبُو الطَّاهِرِ، وَحَرْمَلَةُ، قَالَ أَبُو الطَّاهِرِ أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، قَالَلَمْ يَكُنْ رَسُولُ اللَّهِ صلى الله عليه وسلم يَسْتَلِمُ مِنْ أَرْكَانِ الْبَيْتِ إِلاَّ الرُّكْنَ الأَسْوَدَ وَالَّذِي يَلِيهِ مِنْ نَحْوِ دُورِ الْجُمَحِيِّينَ .
Translation
Salim reported on the authority of his father (Allah he pleased with him) that Allah'& Messenger (tinny peace be upon him) did not touch any of the corners of the House. except that of Black Corner (in which the Black Stone is embedded and that (portion) near it, towards the houses of the tribe of jumuhi.