7 Following the imperative, the cohortative indicates consequence. If Abram is blameless, then the Lord will ratify the covenant. Earlier the Lord ratified part of his promise to Abram (see Gen 15:18–21), guaranteeing him that his descendants would live in the land. But the expanded form of the promise, which includes numerous descendants and eternal possession of the land, remains to be ratified. This expanded form of the promise is in view here (see vv. 2b, 4–8). See the note at and R. B. Chisholm, “Evidence from Genesis,” A Case for Premillennialism, 35–54.
8 Heb “I will multiply you exceedingly, exceedingly.” The repetition is emphatic.

In other versions

that I may make my covenant between me and you, and may multiply you greatly.”

Then I will make my covenant between me and you and will greatly increase your numbers.”

I will set up my covenant between me and you, and I will multiply you greatly.”

I will make a covenant with you, by which I will guarantee to give you countless descendants.”

so that I may make my covenant between me and you, and may multiply you exceedingly.”

And I will make my covenant between me and thee, and will multiply thee exceedingly.

Public Domain