needs must

Then I walked about, till I found on the further side, a great river of sweet water, running with a strong current; whereupon I called to mind the boat-raft I had made aforetime and said to myself, "Needs must I make another; haply I may free me from this strait. If I escape, I have my desire and I vow to Allah Almighty to forswear travel; and if I perish I shall be at peace and shall rest from toil and moil."