It is disliked to seek the help of a disbeliever in wars (except in cases of necessity, or if he thinks well of the Muslims)

Sahih Muslim · Book 32 · Hadith 1817

حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، عَنْ مَالِكٍ، ح وَحَدَّثَنِيهِ أَبُو الطَّاهِرِ - وَاللَّفْظُ لَهُ - حَدَّثَنِي عَبْدُ اللَّهِ بْنُ وَهْبٍ، عَنْ مَالِكِ بْنِ أَنَسٍ، عَنِ الْفُضَيْلِ بْنِ أَبِي، عَبْدِ اللَّهِ عَنْ عَبْدِ اللَّهِ بْنِ نِيَارٍ الأَسْلَمِيِّ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ عَائِشَةَ، زَوْجِ …

It has been narrated on the authority of A'isha, wife of the Prophet (ﷺ), who said: The Messenger of Allah (ﷺ) set out for Badr. When he reached Harrat-ul-Wabara (a place four miles from Medina) a man met him who was kno…