The Quran

وَأَعِدّوا لَهُم مَا استَطَعتُم مِن قُوَّةٍ وَمِن رِباطِ الخَيلِ تُرهِبونَ بِهِ عَدُوَّ اللَّهِ وَعَدُوَّكُم وَآخَرينَ مِن دونِهِم لا تَعلَمونَهُمُ اللَّهُ يَعلَمُهُم ۚ وَما تُنفِقوا مِن شَيءٍ في سَبيلِ اللَّهِ يُوَفَّ إِلَيكُم وَأَنتُم لا تُظلَمونَ

Muhammad Asad

Hence, make ready against them whatever force and war mounts¹ you are able to muster, so that you might deter thereby the enemies of God, whoare your enemies as well,² and others besides them of whom you may be unaware, [but] of whom God is aware; and whatever you may expend³ in God's cause shall be repaid to you in full, and you shall not be wronged.

Lit., "tethering of horses" (ribat al-khayl): an expression which signifies "holding in readiness mounted troups at all points open to enemy invasion (thughur)"; hence, tropically, the over-all maintenance of military preparedness.
Lit., "God's enemy and your enemy" - implying that every "enemy of God" (i.e., everyone who deliberately opposes and seeks to undermine the moral laws laid down by God) is, eo ipso, an enemy of those who believe in Him.
I.e., of resources, efforts and sacrifice of life.