Congress vice president Rahul Gandhi, while addressing a party election rally in Bihar's Madhubani district said the people of Bihar will teach a hard lesson to Prime Minister Narendra Modi in the state assembly polls as he failed to fulfil his promises. 'Modi has failed to fulfil any promises made to the people. High prices of pulses and other essential commodities in the country have angered the people but he is still talking big and doing nothing,' said Rahul Gandhi..