Prasad's remarks came after Ramdev called on him this morning at his residence here.
The bonhomie between the two was apparent during the meeting with Ramdev gifting Prasad a range of Patanjali products and also applying an ayurveda cream on the politico's face - suggestive of their new-found closeness.
Showering praises on Ramdev, Prasad said people are "jealous" of the "huge" success the yoga guru has attained through "sheer hard work".
"Yesterday, I had told him over phone to be careful as he has many enemies now," the RJD president said.
On asked by scribes whether he will promote Patanjali products, Prasad replied in a lighter vein saying, "I am a permanent brand ambassador of his products."
On his part, Ramdev said he had come to invite Prasad for an yoga event.