Money earned

न्यायोपार्जित वित्तस्य दशमांशेन धीमत: । कर्तव्यो विनियोगश्च ईश्वiर प्रीत्येर्थमेव च ।। – स्कंदपुराण
Money obtained by righteous means also becomes pure after offering 10% of it unto God, i.e. for good deeds without expecting any returns. – Skanda Puran