He is accused of dismissing all coronavirus-related warnings and urging people to stay inside the 100-year-old mosque complex in Nizamuddin.
The Tablighi event became India's biggest domestic source of COVID-19.
Tablighi Jamaat, which urges Muslims to lead a life similar to how followers did during the time of Prophet Muhammad, hosted an event in Delhi which was attended by thousands from India and over 200 foreigners.
The foreigners came from coronavirus-infected countries and spread to others.
Carrying the infection, the attendees returned home and authorities spent a great deal of time tracing them.
While some members cooperated in the police probe, others showed reluctance, and a few of them even made the jobs of healthcare workers difficult.
Saad belonged to the non-cooperative bunch and had to be issued notices by Delhi Police.
On April 8, his lawyer Tauseef Khan said he will join the probe only after the quarantine period ends.
To note, Saad was given two notices by Delhi Police asking to vacate the markaz but he ignored both of them.
On March 21, he was told the government has banned large gatherings, so the area must be vacated.
Three days later, when Prime Minister Narendra Modi announced the countrywide lockdown, cops at Hazrat Nizamuddin station spoke with Jamaat officials explaining the health risk.
Not only did Saad ignore almost all rules of authorities, but he also asked Tablighi followers to not fear death.
"Where will you run from death? Death is in front of you...This is an occasion to seek penance from God. Not an occasion where one comes under the influence of doctors and stops Namaaz, meeting each other," he reportedly said about the pandemic.
"Yes, there is a virus. But 70,000 angels are with me and if they can't save me, who will? This is the time for more such gatherings, not the time to avoid each other," he reportedly said in a sermon that police is investigating.
Meanwhile, India's lockdown, the largest in the world, was extended till May 3 today.
Earlier, the Union Health Ministry claimed the restrictions helped in keeping a check at COVID-19 cases.
"According to statistical analysis, in the absence of lockdown and other containment measures, there would have been 41% increase and 8.2 lakh coronavirus cases by April 15," the government said.
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