Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) said: A man came to the Prophet (peace and blessings be upon him) and began asking permission for jihad. The Messenger of Allah (peace and blessings be upon him) asked him: "Are your parents alive?" He said: Yes. He (peace and blessings be upon him) said: "Then strive in (serving) them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17827