Here is the Sanskrit anuvad, Hindi anuvad, and English translation of Jnana-Karma-Sanyasa Yoga Chapter 4, Verse 4.7.
Sanskrit
यदा यदा हि धर्मस्य ग्लानिर्भवति भारत । अभ्युत्थानमधर्मस्य तदात्मानं सृजाम्यहम् ॥ ४.७ ॥
Hindi
हे भारत ! जब-जब धर्मकी हानि और अधर्मकी वृद्धि होती है, तब-तब ही मैं अपने रूपको रचता हूँ अर्थात् साकाररूपसे लोगोंके सम्मुख प्रकट होता हूँ|
English
The Lord declared solemnly unto Arjuna: O Arjuna, whenever good is overcome by evil, or whenever evil manifests itself throughout the world in such a way that good no longer exists. I will always appear on earth.