Hadithcore
Mishkat al-Masabih, 3817

‘Abdallah b. ‘Amr told that a man came to God’s Messenger and asked his permission to take part in <i>jihad</i>. He asked him if his parents were still alive, and when he replied that they were, he told him to exert himself* on their behalf. *The point is not so clear in English as in Arabic. <i>Jihad</i>, while being the word for fighting against infidels, also means to strive or to exert oneself in general. The man wished to take part in <i>jihad</i>, and when the Prophet (ﷺ) heard that his parents were still alive he said <i>fa-fihima fa-jahid</i> (exert yourself on their behalf.) (Bukhari and Muslim.) A version has, “Return to your parents and look after them well.”

وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ: جَاءَ رَجُلٌ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَاسْتَأْذَنَهُ فِي الْجِهَادِ فَقَالَ: «أَحَي والدك؟» قَالَ: نَعَمْ قَالَ: «فَفِيهِمَا فَجَاهِدْ» . مُتَّفَقٌ عَلَيْهِ. وَفِي رِوَايَةٍ: «فَارْجِعْ إِلَى وَالِدَيْكَ فَأَحْسِنْ صُحْبَتَهُمَا»

References1 variant
In-Book Reference
Book 19, Hadith 30