Here's a link to a primary source that literally has Deus Vult in it. This is an account of the speech of Pope Urban II from 1095 in Clermont, when he called for the first crusade.
https://sourcebooks.fordham.edu/source/urban2a.asp
https://sourcebooks.fordham.edu/source/urban2a.asp
"Most beloved brethren, today is manifest in you what the Lord says in the Gospel, `Where two or three are gathered together in my name, there am I in the midst of them'; for unless God had been present in your spirits, all of you would not have uttered the same cry; since, although the cry issued from numerous mouths, yet the origin of the cry as one. Therefore I say to you that God, who implanted is in your breasts, has drawn it forth from you. Let that then be your war cry in combats, because it is given to you by God. When an armed attack is made upon the enemy, this one cry be raised by all the soldiers of God: 'It is the will of God! It is the will of God!' [Deus vult! Deus Vult!]