Tatarstan's top Islamic leader offered words of forgiveness and asked police to act objectively after attackers bombed his car and killed a colleague last week.
"I forgive those who committed this wickedness. Allah will justly determine a fair punishment for what they have done," Mufti Ildus Faizov said, according to a statement on the republic's Spiritual Board of Muslims website.
Faizov said people often act through ignorance and naivety.
"In such cases, we should show mercy, be able to forgive," he said.
The 49-year-old Muslim spiritual leader received multiple injuries, including two broken legs, after assailants detonated three car bombs in his SUV in Kazan on June 19, a day before the Muslim holy month of Ramadan.
Valiulla Yakupov, a prominent cleric who headed the Spiritual Board of Muslims' education department, died minutes earlier after being shot by unidentified gunmen outside his house in Kazan.
President Vladimir Putin has promised that the perpetrators will be punished.
Faizov described Yakupov as "one of the most important Muslim preachers in the country" and praised him for his work in rebuilding Kazan's Apanai mosque and writing religious publications.
He also called on law enforcement officers to investigate the attacks objectively "without infringing on the rights of our brothers and sisters."
Faizov's appeal comes as two Islamic organizations plan to demonstrate and rally on July 29 against what they see as the illegal detention of Muslims in connection with the attacks.
Officially, police have arrested only six Tatarstan residents in connection with the attacks, but local organizations say hundreds of Muslims have been detained and are being questioned.
Nail Nabiullin, head of the Al-Ikhlas mosque in Kazan, said police had detained 400 to 600 Muslims and conducted about 160 raids, Interfax reported.
"Law enforcement structures should stop their hack job. The principle 'grab everyone in succession' is causing even greater distrust toward the police among the population," Nabiullin said.
He added that even if authorities deny permission for the rally, people will take to the streets to express their discontent.