Āraṇyaka-parva Adhyāya 277 — Sāvitrī-Upākhyāna: Aśvapati’s Vows and Sāvitrī’s Birth; Search for a Suitable Husband Begins
तदर्थमवतीर्णो सौ मन्नियोगाच्चतुर्भुज: । विष्णु: प्रहरतां श्रेष्ठ: स तत् कर्म करिष्यति,उस राक्षसके निग्रहके लिये मैंने चतुर्भुज भगवान् विष्णुसे अनुरोध किया था। मेरी प्रार्थनासे वे भगवान् भूतलपर अवतार ले चुके हैं। वे योद्धाओंमें श्रेष्ठ हैं; अत: वे ही रावणके दमनका कार्य करेंगे
tadartham avatīrṇo sau manniyogāc caturbhujaḥ | viṣṇuḥ praharatāṃ śreṣṭhaḥ sa tat karma kariṣyati ||
Markandeya said: “For that very purpose, at my request, the four-armed Lord Viṣṇu has descended to the earth. He is the foremost among those who strike down the wicked; therefore he himself will accomplish the task—bringing about the suppression of Rāvaṇa.”
मार्कण्डेय उवाच
When adharma becomes oppressive, the restoration of order may require a divinely guided response: the protector (Viṣṇu) descends not for personal gain but to uphold dharma and restrain destructive power.
Mārkaṇḍeya explains that, to deal with the rākṣasa menace—specifically Rāvaṇa—he petitioned Viṣṇu, who has now incarnated on earth and will carry out the work of subduing him.