Mata Ganga who was the wife of Guru Arjan Dev Ji, could not have a baby, so she went to ask Bhai Budha for this blessing. After rejecting her once, Bhai Budha accepted her offering. As he ate he crushed an onion with his fist, he said, "Your son will be a master of heaven and earth. He will crush enemies like I crushed this onion."
When Nanak was a little boy he went to school, and he wasn't interested in learning the alphabet. He only wanted to chant Gods name. His teacher asked him to recite the alphabet and Guru Nanak recited it without ever being taught. The teacher was so impressed that he fell to his knees and bowed to the young Nanak.
Humayun went to Guru Angad to get blessing and restore his rule. He got angry that the Guru didn't give him respect so he went to kill the Guru. Then Guru Angad told him that he is quick to kill men of God, but couldn't defend his on kingdom. Humayun bowed to the Guru and asked forgiveness.