Now ye have delivered the children of Israel out of the hand of the Lord. The word here rendered "now" is rather then. But the Hebrew word, like our own, is used as implying not only consecution of time, but consequence of action (see Psalms 40:8; Psalms 69:5; Jeremiah 22:15).
Thus the meaning here is, "We see, then, that instead of bringing upon us heavy chastisement, as we had feared, ye have acted in a way which secures us from the punishment of which we were afraid."