With permission from Rama, Lakshman attacked the brave Indrajit and they fought a mighty duel. When Indrajit realized he was not able to overpower Lakshman instead he was getting tormented by him, he used the mighty weapon of Shakti on him. Lakshman fell down in a faint. Indrajit tried to lift the unconscious Lakshman in his arms, but try as he might, he could not do so. Embarrassed, he went away. When Hanuman realized that Lakshman has fainted, he picked him up on his shoulders and took him to Shri Rama. When he saw Lakshman in that state, Rama cradled him in his lap and cried loudly. The entire vanara army was plunged in sorrow and despair.
Vibheeshan consoled Rama and told him to get the physician Sushena from Lanka to treat Lakshman. Hanuman went to in the dark of the night to the city of Lanka and brought back Sushena with him. The vaid (physician) examined the pulse of Lakshman and said that there is a herb that can revive him but it only on the peak of a mountain in the Himalayas. If that herb, ‘Sanjeevani booti’ was not brought before sunrise, then it was possible that Lakshman would not survive the power of the Shakti weapon that had felled him.
With the permission of Rama, Hanuman journeyed to the Himalayas through the air.
When Ravana learned from his spies that Hanuman has gone to get the Sanjeevani herb from the Himalayas, he went to the mayavi magician Kalnemi and told him to use his magical powers to halt Hanuman on his way to the Himalayas and kill him with a deceitful plan. Kalnemi went off to obey Ravana’s orders.
Lakshman Seriously Injured, Ramayana – The Epic Story