A.T. Robertson Commentary Hebrews 6:14

"saying, Surely blessing I will bless thee, and multiplying I will multiply thee." — Hebrews 6:14 (ASV)

Surely (ε μην). By itacism for η μην (Deissmann, Bible Studies, p. 205). The quotation is from Ge 22:16f. (the promise renewed to Abraham with an oath after offering of Isaac).

Blessing (ευλογων). Hebraism (present active participle) for the Hebrew infinitive absolute and so with πληθυνων (multiplying).