The appearance of the Lord is manifested for the annihilation of the upstarts. His activities are transcendental and are enacted for the understanding of all persons. Otherwise, since the Lord is transcendental to all material modes, what purpose could He serve by coming to earth?
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
अजस्य जन्मोत्पथनाशनाय कर्माण्यकर्तुर्ग्रहणाय पुंसाम् । नन्वन्यथा कोऽर्हति देहयोगं परो गुणानामुत कर्मतन्त्रम्
ajasya janmotpathanāśanāya karmāṇyakarturgrahaṇāya puṃsām | nanvanyathā ko'rhati dehayogaṃ paro guṇānāmuta karmatantram
SB 3.1.44