Rashi cites the Talmud in Sanhedrin 89b which explains that these words apply to the “words” of the Satan. The Satan attempted to condemn Avraham for not offering a sacrifice to Hashem during the plentiful banquet he had arranged in honor of Yitzchak. Hashem responded to the Satan, “Even if I had told him to sacrifice his own son, he would do it! Did he not make the whole banquet in honor of his son?” Hashem immediately commanded Avraham to perform the Akeidah. The fact that Avraham did not offer any form of sacrifice seems puzzling. While he had the faith and moral stamina to withstand the trial of the Akeidah, he did not offer a korban in thanksgiving to Hashem during the banquet in honor of Yitzchak.
Be’er Yosef suggests the following explanation for Avraham’s behavior. Avraham’s aspiration in having progeny was to fulfill a single goal, the perpetuation of the monotheistic belief in Hashem. When Yitzchak was born, the source of Avraham’s enjoyment was the hope that the continuity of his life’s work would now be realized. There was no personal motive in this wonderful banquet he prepared in honor of Yitzchak’s birth. Rather, it was a seudas mitzvah in the holiest degree. There was no need for a physical manifestation of sacrifice at this banquet. The whole banquet was in his son’s honor, as he was perpetually prepared to “sacrifice” this wonderful son in the service of Hashem. There was no need for a specific ritual “sacrifice” when the the entire orientation of the banquet was sacrifice.