The Gospel tells us that Jesus Christ died for our sins, was buried, and rose from the dead. This verse points out particularly how He died. The manner of His death testifies to its significance in God's plan of salvation.
Death on a cross was the ultimate punishment of the law breaker. It involved great suffering in death. (Read Psalm 22.) Crucifixion was reserved for certain crimes. In any just administration there is a direct connection between the seriousness of the crime and the severity of the punishment. The cross witnesses then to the seriousness of our sins in God's sight.
Our culture has become calloused to the uncleanness and the violence of the growing sin in our world. However, God declared how serious it was to Adam from the beginning by the punishment promised. "thou shalt surely die" (Genesis 2:17d). And in God's administration, this includes eternal torment for those who die in their sins. "And death and hell were cast into the lake of fire. This is the second death" (Revelation 20:14). Jesus paid a horrible price to provide salvation because sin is a horrible thing in God's sight and has a terrible punishment.
Death on a cross was also a public punishment. The sufferer was lifted up for all to look upon. This teaches us faith. We must look to the Saviour and His sacrifice alone for our salvation. "And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up: That whosoever believeth in him should not perish, but have eternal life. For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life" (John 3:14-16).