Charles Ellicott Commentary Isaiah 56:8

"The Lord Jehovah, who gathereth the outcasts of Israel, saith, Yet will I gather [others] to him, besides his own that are gathered." — Isaiah 56:8 (ASV)

The Lord God ... says. —The phrase is the normal one for introducing an oracle of special importance. This, so to speak, was to be one of the “faithful sayings” of Isaiah. We can hardly fail to find in John 10:16 a deliberate reproduction of Isaiah’s thought. The first clause refers clearly to the gathering of the heathen as following on that of the “outcasts” of Israel.