On the seventh day after the Buddha’s homecoming Princess Yasodhara dressed up young Rahula. The Buddha’s son had been brought up by his mother and grandfather and was now seven years old. She pointed to the Buddha and said, “That is your father, Rahula. Go and ask him for your inheritance.”
Innocent Rahula went to the Buddha and, looking up into his face, told him what his mother had asked him to say, adding, “Father, even your shadow is pleasing to me.”
As the Buddha left the palace Rahula followed him saying, “Give me my inheritance.” Coming to the park the Buddha thought, “He desires his father’s wealth, but this goes with the worldly life and is full of trouble and suffering. I shall instead give him what I know and thus give him an excellent inheritance.” The Buddha then asked Sariputta, one of his disciples, to ordain Rahula.
When King Suddhodana heard that his beloved grandson had become a monk he was deeply grieved. The king said, “When you left home it made me sad. When Nanda left home my heart ached. I concentrated my love on my grandson and again the one I love has left me. Please do not ordain anyone without their parent’s permission.” To this the Buddha agreed and never ordained anybody after that without their parents’ permission. Link source