Sunan Abi Dawud Book 15, Hadith 55
When the Messenger of Allah (ﷺ) went on an expedition, he took Umm Sulaym, and he had some women of the Ansar who supplied water and tended the wounded.
A man emigrated to the Messenger of Allah (ﷺ) from the Yemen. He asked (him): Have you anyone (of your relatives) in the Yemen? He replied: My parents. He asked: Did they permit you? He replied: No. He said: Go back to them and ask for their permission. If they permit you, then fight (in the path of Allah), otherwise be devoted to them.
The Prophet (ﷺ) said: Three things are the roots of faith: to refrain from (killing) a person who utters, "There is no god but Allah" and not to declare him unbeliever whatever sin he commits, and not to excommunicate him from Islam for his any action; and jihad will be performed continuously since the day Allah sent me as a prophet until the day the last member of my community will fight with the Dajjal (Antichrist). The tyranny of any tyrant and the justice of any just (ruler) will not invalidate it. One must have faith in Divine decree.