God is often described as “gracious and merciful” (Ps 111:4). The pairing shows God’s undeserved favor out of a heart that knows our need and seeks to bring relief.
The One who is “high and lifted up” (57:15) tells us all we need to know about him. We need an accurate estimation of the Almighty. Isaiah had a hard message for a hard people. He needed a high view of God to sustain him in difficult ministry.