When the service ended, the parishioners in their Sunday best walked home through neighborhoods still teetering on a knife's edge.
Just after the service, around the corner from the church, the intimidation went on: An angry, wild-eyed young man with a machete shouted at a woman standing by her gate.
She cringed, terrified, as he whacked her with the flat of the blade.
With no sign of a solution to Kenya's political impasse, an opposition rally planned for Tuesday has raised fears of a new increase in killings.
Last month's presidential election unleashed tribal violence across Kenya, pitting Luos and others who support opposition leader Raila Odinga against Kikuyus and their allies who support President Mwai Kibaki.
Odinga accuses Kibaki of stealing the Dec. 27 election. Western observers said the poll did not meet democratic standards. More than 300 people have died in the violence.
As one parishioner, Rebecca Muthoni, a 38-year-old Kikuyu, plodded to the Lutheran church Sunday, her heart was heavy. Muthoni's shack and the kindergarten where she taught children had been burned, as well as her church.
As Pastor Dennis Meeker prayed, she fell to the ground, tears flowing from her eyes, crying out hysterically: "Forgive them! Forgive them!"
As she yelled, Meeker repeated over and over, "We shall persevere."
"My pain is really deep," she said after the service. "I am feeling bad in my heart. I have no house and no job. And I am the only breadwinner in the family."
The fire spared the church walls, but there was a black scar on the wall behind the altar with a white patch in the center. Meeker plans to leave it there to remind people what happened in Kibera over the last week: To him, the black mark represents Christ's descent to hell and the white patch his resurrection. Meeker said the attacks could destroy the building but not the church, and urged the congregation to forgive.
Meeker, an American who arrived from Iowa in September, has faced his own inner struggle since the church was burned Thursday by looters during opposition protests.
"You struggle with anger. You struggle with weeping," he said. "I don't think you can make sense out of it. In fact, this is caused by politicians because we were really living in peace and going along well until the presidential election."
The congregation is drawn from a mix of tribes, but about half the parishioners did not come to church Sunday, given the violence in the area.
"I think it is going to get worse because [the political leaders] are both standing firm. They don't want to walk the way of peace," Meeker said.
"Kenya is going to bow down to really bad things if they're not careful. There's going to be a lot of hatred and a lot of killings."
Severe food shortages in Kibera and other slum districts have fueled the instability, particularly in Luo areas, where there is deep anger over the elections.
Nairobi has long been the thriving capital of East Africa's strongest economy, so the last week's chaos has brought a new sight: thousands of desperate people lined up at food distribution centers, pushing and jostling for aid.