By Ráma’s high behest to her I go a willing messenger; And never shouldst thou hinder one Who toils for Daśaratha’s son. First captive Sítá will I see, And him who sent and waits for me, Then come and to thy will submit, Yea, by my truth I promise it.”

In plain words: Hanuman says he is going to Sita as Rama's willing messenger and should not be stopped. He promises on his honour that after he finds Sita and reports to Rama, he will come back and let her eat him.