Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates from the Prophet (peace and blessings be upon him): "'Al-'aynu haqq' (The evil eye is real). If anything were to outstrip the decree, it would be the evil eye; and when you are asked to wash, then wash."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19614