"Faith comes from hearing, and hearing by the word of Christ" (Ro 10:17). Is the Old Testament less relevant than the New Covenant? When you consider that what happened to Israel was "written for our instruction" (1Co 10:11) it is applicable. We are no different than them. "Elijah was a man with a nature like ours" (Jas 5:17). They had to follow God themselves and God doesn't change (Mal 3:6). "They were drinking from a spiritual rock which followed them; and the rock was Christ" (1Co 10:4).
God led Israel "performing wonders and signs in the land of Egypt and in the Red Sea and in the wilderness for forty years" (Ac 7:36). "He led them with the cloud by day, and all the night with a light of fire" (Ps 78:14). The Lord said, "'Assemble the people to Me, that I may let them hear My words so they may learn to fear Me all the days they live on the earth'" (Dt 4:10). Moses said, "'You, O Lord, have been seen face to face, that your cloud stays over them, and that you go before them'" (Nu 14:14). Later he said, "'Has anything been heard like it? Has any people heard the voice of God speaking from the midst of the fire, as you have heard it, and survived?'" (Dt 4:32-33). "'To you it was shown that you might know that the Lord, He is God; that there is no other besides Him'" (:35).
Therefore, when we read this we, too, can comprehend. It provides the faith we need. "'Only give heed to yourself and keep your soul diligently, so that you do not forget the things which your eyes have seen and they do not depart from your heart all the days of your life'" (Dt 4:9).