John Gill Commentary Nehemiah 9:38

"And yet for all this we make a sure covenant, and write it; and our princes, our Levites, [and] our priests, seal unto it." — Nehemiah 9:38 (ASV)

And because of all this
Of all this distress, and that it might be removed, and be clear of it; or "in all this distress and evil", as Jarchi and Aben Ezra, in the midst of it all:

we make a sure covenant ;
or faithfully promise to observe the law of God, and particularly put away strange wives, and not intermarry with the people of the land:

and write it ;
that it may remain and be a testimony against them should they break it, being their own handwriting:

and our princes, Levites, and priests, seal unto it ;
as witnesses of it, and thereby binding themselves to observe the same things; their names that sealed are given in the next chapter.