Ibn Abbas saw Abdullah bin Harith praying with his hair tied in a knot behind his head, so he stood up and began to undo it. When Abdullah finished his prayer, he turned to Ibn Abbas and asked, "What concern do you have with my hair?"Ibn Abbas replied, "I heard the Messenger of Allah ﷺ say, 'The likeness of one who prays in this state is like that of someone praying with his hands tied behind his back.'"
أنه رأى عبد الله بن الحارث يصلي ورأسه معقوص من ورائه. فقام فجعل يحله. فلما انصرف أقبل إلى ابن عباس. فقال: مالك ورأسي؟ فقال: إني سمعت رسول الله ﷺ يقول: إنما مثل هذا مثل الذي يصلي وهو مكتوف.
Narrated by Muslim in the Book of Prayer (492), from Amr bin Sawad Amiri, who reported, "Abdullah bin Wahb informed us, Amr bin Harith informed us, that Bukayr told him, that Kurayb, the freedman of Ibn Abbas, told him, on the authority of Abdullah bin Abbas," and he mentioned the hadith.His saying "maqus" carries the same meaning as "maktuf," as mentioned earlier, meaning hair gathered up in the middle of the head. This also involves resembling the practice of women. The prohibition against holding back one's hair and garment has already been discussed.Ibn Athir said in Nihayah (3/275) regarding the meaning of the hadith of Ibn Abbas, "He meant that if the hair is left loose, it falls to the ground during sujud, and its owner is thereby given the reward of sujud performed with it. But if it is gathered up, it becomes as though it had not prostrated at all. He likened this to being 'maktuf,' meaning having one's hands bound, since in that case they cannot reach the ground during sujud."