A.T. Robertson Commentary 2 Corinthians 6:18

"And will be to you a Father, And ye shall be to me sons and daughters, saith the Lord Almighty." — 2 Corinthians 6:18 (ASV)

Saith the Lord Almighty (λεγε Κυριος παντοκρατωρ). 2 Samuel 7:8. This use of εις is a Hebraism for Hebrew le instead of predicate nominative. Παντοκρατωρ (πασ, κρατεω, Ruler of all) is common in the LXX. Occurs also in the inscriptions and papyri. In the N.T. only here and in Revelation.