What does Isaias Chapter 40 say, and which statements belong to its speaker?

Isaias 40 calls for comfort to God's people and speech to Jerusalem's heart: evil ends, iniquity is forgiven and double is received for sins. A desert voice calls for the Lord's straight way, raised valleys and lowered mountains, with crooked places straight and rough places plain. All flesh sees glory. Asked what to cry, the voice compares flesh and glory with grass and flower: the Lord's spirit withers them, but God's word endures.

The bearer of good tidings is called up the mountain and told to proclaim God to Juda's cities without fear. Strength, reward and work before him accompany his coming. A shepherd feeds his flock, gathers lambs in his arms and bosom, and carries those with young. Water in the hand, heaven measured by the palm, earth's bulk by three fingers and weighed mountains and hills lead to questions about any counsellor or teacher of God.

Gentiles are like a bucket's drop and the smallest balance grain; islands are dust. Libanus and its animals cannot provide a sufficient offering. Nations are nothing and vanity before him. A cast statue with gold and silver plates, or durable wood chosen by the poorer person, supplies the idol comparison. God sits upon earth's globe, inhabitants like locusts, and stretches heaven as nothing and a tent. Searchers of secrets and judges are brought to nothing, barely planted or rooted before the whirlwind carries them away.

The host is brought forth by number and called by name, none missing. Jacob's complaint about hidden way and overlooked judgment receives an answer: the everlasting creator neither faints nor labors, and his wisdom is unsearchable. He gives strength to the weary and force to those lacking it. Youths tire and young men fall, while those hoping in him renew strength with eagle wings, running and walking without fatigue. These are attributed prophetic assurances, not a medical guarantee of unlimited stamina.