(a) It is reported through another chain that Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: Doing so is ikhlas (sincerity).
(b) It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him): Doing so is humility.
(c) Uthman narrates from Mujahid (may Allah have mercy on him): It is a hammer against Satan.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2795