Then Abraham forsook his father in Haran, and journeyed to Canaan, accompanied by the blessing of God, who said unto him, "I will make of thee a great nation, and I will bless thee, and make thy name great." These three blessings were to counteract the evil consequences which, he feared, would follow emigration, for travelling from place to place interferes with the growth of the family, it lessens one's substance, and it diminishes the consideration one enjoys.
The greatest of all blessings, however, was the word of God, "And be thou a blessing." The meaning of this was that whoever came in contact with Abraham was blessed. Even the mariners on the sea were indebted to him for prosperous voyages. Besides, God held out the promise to him that in time to come his name would be mentioned in the Benedictions, God would be praised as the Shield of Abraham, a distinction accorded to no other mortal except David.
But the words, "And be thou a blessing," will be fulfilled only in the future world, when the seed of Abraham shall be known among the nations and his offspring among the peoples as "the seed which the Lord hath blessed."