Today's OT reading (Judges 19-21) is the most repulsive story in the Bible. It is not repulsive because the Bible is bad, but because people are bad. It contains the worst elements of sinful humanity: sexual perversion, brutality, stubbornness, cruelty, impudence.
It begins with a Levite from Ephraim tracking down a run-away concubine. As they return home, they stop in the city of Gibeah (in the territory of Benjamin), where no one offers to take care of them. Eventually a fellow Ephraimite who happened to be staying in the city took them in. What follows is a nightmare. The men if the city demand to gang rape the Levite. In desperation the man and the Levite give the mob the concubine, who is abused all night and falls dead at the threshold (was she begging to be let back in? what a horror!). The Levite dismembered her, sending a grisly message to each tribe to let them know what had happened.
The tribes were outraged, and demanded that Benjamin punish the men of Gibeah. Not only did the Benjamite refuse, they mustered for battle, and at the end of the incredibly bloody conflict 40,000 Israelites were dead and nearly all of the men of Benjamin were annihilated (25,100 of 26,000). The book concludes with Israel trying to find a way around its impudent vow not to marry anyone from Benjamin, leading to the brutal invasion of Jabesh-gilead and the kidnapping of hundreds of women for the survivors of Benjamin to marry.
The book of Judges began with the story of Israel's efforts to subdue to the Canaanites. It ends with a tribe of Israel nearly wiped out like the Canaanites were supposed to have been, a sad reminder than in many ways Israel had become indistinguishable from Canaan.
However, today's NT reading (Acts 2) presents a much different picture. Instead of Israel at war with itself, Jews from every nation under heaven were gathered in one place, and by the miracle of tongues able to hear the message of the gospel. And that message was not just for Israel, but for "whoever calls on the name of the Lord." By the end of the chapter, thousands of new Christians "were together and had all things in common."
This is the power of the gospel. It reconciles sinful men with God, and with each other.