And it came to pass, that when Isaac was old
He is generally thought to be about one hundred and thirty seven years of age at this time, which was just the age of his brother Ishmael when he died, ( Genesis 25:16 ) ; and might put him in mind of his own death as near at hand; though if he was no older, he lived after this forty three years, for he lived to be one hundred and eighty years old, ( Genesis 35:28 ) : and his eyes were dim, so that he could not see;
which circumstance is mentioned, not only as a sign of old age, and as common to it, but for the sake of the following history, and as accounting for it, that he should not know Jacob when he blessed him; and this was so ordered in Providence, that by means of it the blessing might be transferred to him, which otherwise in all probability would not have been done, if Isaac had had his sight: he called Esau his eldest son;
who though he was married, and had been married thirty seven years at this time, yet still lived in his father's house, or near him; for as he was born when his father was sixty years of age, and he married when he himself was forty, and his father must be an hundred, so if Isaac was now one hundred and thirty seven, Esau must have been married thirty seven years; and though he had disobliged his father by his marriage, yet he retained a natural affliction for him; nor had he turned him out of doors, nor had he any thoughts of disinheriting him; but on the contrary intended to bestow the blessing on him as the firstborn, for which reason he is here called "his eldest son": and said unto him, my son;
owning the relation, expressing a tender affection for him, and signifying he had something further to say unto him: and he said unto him, behold, [here am] I;
by which Esau intimated he was ready to hear what his father had to say to him, and was willing to obey him. The Targum of Jonathan says, this was the fourteenth of Nisan, when Isaac called Esau to him.