(8) The fourth angel poured out his bowl on the sun, and it was allowed to scorch people with fire.
The Lord told Israel that if they obey not the covenant which he made with them that he would strike them with fiery heat (Deuteronomy 28:22), and here we see this envisioned in the figure of the sun scorching them with fire. The fiery heat which the Lord promised was in the way of a scorching hot illness of the body and a scorching of the crops (ibid). This verse, like most of this book, reminds us that God has not forgotten the words he spoke long ago to this people by his servant Moses.
(9) They were scorched by the fierce heat, and they cursed the name of God who had power over these plagues. They did not repent and give him glory.
This verse gives us a visual of the character of the nation; no matter how much pain is inflicted upon them, they will never humble themselves before their God. This verse does another thing for us; it explains that God would still be willing to grant them forgiveness, if they would only repent. With this scorching heat, they are feeling the very opposite of what they could be feeling if they were numbered with the faithful. For the lives of the faithful were earlier described in cool comfort, “the sun shall not strike them, nor any scorching heat.” (7:16).