Khanna passed away at the age of 70 on April 27 after battling cancer.
Several Bollywood stars including Amitabh Bachchan, Shah Rukh Khan, Aamir Khan, Hrithik Roshan, Sonakshi Sinha, Farhan Akhtar, Zoya Akhtar, Arbaaz Khan, Tabu, Kiran Rao, Madhuri Dixit, Hema Malini, Sridevi, Boney Kapoor among others had attended the prayer meet.
"Thank you my film brethren for your solidarity shown towards the Khanna family. Hum mein ab bhi insaniyat baaki hai (there is still humanity left in us) Love you all," Rishi posted.
Earlier, Rishi had slammed the "actors of this generation" for their absence at Khanna's funeral.
Kapoor, 64, who worked with Khanna in films like "Amar Akbar Anthony" and "Chandni", described the absence of the young generation of stars at the cremation as "shameful".