Theodoret of Cyrus, on Isa 51:2

“Look unto Abraham your father, and to Sara that bore you: for I called him alone, and blessed him, and multiplied him.”

“He is leaving aside the unbelievers here in order to address those who have believed: it is to them that he gives the name of enamored with God and with righteousness. He comforts them because they are few in number and invites them to turn their eyes toward their ancestors: he reminds them of Abraham and Sarah and the many thousands of descendants who came from them. This is similar to the term expressed in the divine Gospels: "Do not fear, little flock, for it is your Father's good pleasure to give you the kingdom." It is the same here.”

Imported from an open dataset — not yet checked against the printed edition.