and to give relief to you that are afflicted with us, when the Lord Jesus is revealed from heaven with his mighty angels in flaming fire,
The word "rest" (anesis) indicates a loosening or relaxing. Thayer comments this word means "to let loose, slacken, anything tense, for example a bow...more specifically in this passage relief, rest" from persecutions (44-2-425). The word "rest" is not to indicate the Jews or Gentiles would have rest during this life, but their rest would come upon receiving their reward in Heaven (see Hebrews 4:9). The word "rest" denotes freedom and always is used in contrast with afflictions (2 Corinthians 2:13; 2 Corinthians 7:5; 2 Corinthians 8:13). The New Testament teaches "there remains a Sabbath rest for the people of God" (Hebrews 4:9; Revelation 14:13). Paul promises the afflicted Thessalonians that God will grant rest to them. Paul knows what it is to be under tension as he has experienced such at Thessalonica and in other places. It is indeed a pleasant thought to "rest with" the apostles while in Heaven with God, Jesus, and the holy beings. Heaven is spoken of as a place of rest, peace, and comfort (see Luke 16:25; John 14:1-3; Hebrews 4:9; Revelation 6:11; Revelation 21:4).