Here is the Sanskrit anuvad, Hindi anuvad, and English translation of Jnana-Karma-Sanyasa Yoga Chapter 4, Verse 4.8.
Sanskrit
परित्राणाय साधूनां विनाशाय च दुष्कृताम् । धर्मसंस्थापनार्थाय सम्भवामि युगे युगे ॥ ४.८ ॥
Hindi
साधु पुरुषोंका उद्धार करनेके लिये, पापकर्म करनेवालोंका विनाश करनेके लिये और धर्मकी अच्छी तरहसे स्थापना करनेके लिये मैं युग-युगमें प्रकट हुआ करता हूँ|
English
O Arjuna, I appear on earth from time to time for three main purposes. The first is for the protection and preservation of all that represents good, and of all those pure and saintly people on earth. The second purpose for which I appear on earth is for the destruction and removed and wrong-doers.
The third purpose is, of course, for the establishment and creation (or recreation) of Dharma (Righteousness or reinstating moral values among people on earth.)