Saying, Surely blessing I will bless thee - That is, I will certainly bless thee. The phrase is a Hebrew mode of expression, to denote emphasis or certainty - indicated by the repetition of a word; compare Genesis 14:23; Exodus 8:10; Joel 3:14; Judges 5:30; Judges 15:16.
Multiplying I will multiply thee - I will greatly increase thee - I will grant thee an exceedingly numerous posterity.