Charles Ellicott 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)

Because of all this. —On the basis of this confession, and to prove our sincerity.

Seal to it. —On the sealed [document]. Each party impressed his seal on moist clay, which was then hardened. Sometimes these seals were attached to the document by separate strings. In Nehemiah 11:0, “those who sealed” is, literally, those on the sealed [documents], in the plural.