Valmiki Ramayana Aranya Kanda Sarga 32 Shloka 14

यः such (Ravana), कैलासपर्वतम् mount Kailasa, गत्वा on going, नरवाहनम् Kubera, विजित्य having conquered, तस्य his, कामगम् which can fly at the rider's desire, पुष्पकम् aerial chariot called Pushpaka, जहार took away forcibly.

Ravana went to mount Kailasa, conquered Kubera and took away forcibly his aerial chariot Pushpaka which can fly as per the rider's desire