पुरुषस्येह जातस्य भवन्ति गुरवस्त्रयः । आचार्य श्चैव काकुत्स्थ पिता माता च राघव ॥

श्रीमद्वाल्मीकिरामायणे अयोध्याकाण्डे एकादशोत्तरशततमस्सर्गः (२ श्लोक)

“Every human will have three Gurus: mother, father (because they gave birth and nourished you) and Aacharya (because he gives gnyaanam). (hence they must be served relentlessly with utmost respect)” told the great Brahmarshi Vasishtha to ShriRaama.