Charles Ellicott Commentary Isaiah 30:15

"For thus said the Lord Jehovah, the Holy One of Israel, In returning and rest shall ye be saved; in quietness and in confidence shall be your strength. And ye would not:" — Isaiah 30:15 (ASV)

In returning and rest ... —The words describe a process of conversion, but the nature of that conversion is determined by the context. In this case it was the turning from the trust in man, with all its restless excitement, to a trust in God, full of calmness and of peace.