The great Manu, O king of kings, has written two Slokas. As regards your duties, O you of Kuru's race, you should always remember them. Fire has originated from water, the Kshatriya from the Brahmana, and iron from stone. The three, viz., fire, Kshatriya, and iron, can act on every other thing, but coming into contact with their respective origins, their force becomes neutralised.
मनुना चैव राजेन्द्र गीतौ श्लोकौ महात्मना। धर्मेषु स्वेषु कौरव्य हृदि तौ कर्तुमर्हसि॥ अद्भ्योऽग्निर्ब्रह्मतः क्षत्रमश्मनो लोहमुत्थितम्। तेषां सर्वत्रगं तेजः स्वासु योनिषु शाम्यति॥