It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he heard the Messenger of Allah (peace and blessings be upon him) say: "When a servant prays and does not complete its humility (khushu') and its bowing, and keeps looking about, his prayer is not accepted. And whoever drags his garment (on the ground) out of pride, Allah will not look at him (with mercy) on the Day of Resurrection, however honoured he may be in the sight of Allah."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9743