عَنِ ابْنِ عَبَّاسٍ قَالَ: كَانَ لِنَعْلِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قِبَالَانِ مُثَنًّى شراكهما. رَوَاهُ التِّرْمِذِيّ

Ibn Abbas said it is part of the sunna that when a man sits down he should take off his sandals and place them at his side. Abu Dawud transmitted it.