This excerpt is taken from Sheikh Abi Abdul Saboor Abdul Ghafoor Damni's book Fazail al-Jihad.
أخبرنا طلحة بن أبى سعيد قال سمعت سعيد المقبري يحدث أنه سمع أبا هريرة رضى الله عنه يقول قال النبى صلى الله عليه وسلم من احتبس فرسا فى سبيل الله إيمانا بالله وتصديقا بوعده فإن شبعه وريه وروثه وبوله فى ميزانه يوم القيامة.
"Talha bin Abi Saeed narrated to us, he said I heard Saeed Maqbari narrate that he heard from Abu Hurairah (may Allah be pleased with him), who said that the Prophet Muhammad (peace be upon him) said: 'Whoever raises a horse for Jihad in the way of Allah, believing in Allah and confirming His promise, then the horse's food, drink, urine, and dung will be weighed on the Day of Resurrection, and he will be rewarded for all of it.'"
Reference: (Sahih Bukhari and Muslim) (Narrated by Bukhari, Book of Jihad and Expedition, Chapter: Whoever restrains a horse in the way of Allah, Number: 2853)
Explanation
Although this hadith mentions raising horses for the defense of the region, it can also be inferred that in the present era, manufacturing weapons, purchasing them for the defense of the region, protecting them, practicing their use, etc., are also permissible. Providing them will also be a cause of reward, similar to the provision of horses during the time of the Prophet.
