Sayyiduna Ibn Abbas (may Allah be pleased with them both) saw Sayyiduna Abdullah bin al-Harith (may Allah be pleased with him) praying while his hair was tied up behind him. He stood behind him and began to undo it, and the other (that is, Abdullah bin al-Harith) remained still. When he finished the prayer, he came to Sayyiduna Ibn Abbas (may Allah be pleased with them both) and asked: "What business did you have with my head?" He said: "I heard the Messenger of Allah (peace and blessings be upon him) say: 'The likeness of this (one who prays in this way) is that of a person who prays with his hands tied.'"
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12122