A letter from the head of the Catholic Church in England and Wales was read at the funeral of a teenager killed on his way home from a school prom.
Kajetan Migdal, 18, died of his injuries in hospital after the attack in Stevenage, Hertfordshire, on 27 May.
His funeral Mass, at St Hugh of Lincoln Roman Catholic Church in Letchworth, was attended by about 700 mourners.
The Archbishop of Westminster, Cardinal Vincent Nichols, expressed "deep sadness" at his "tragic death".
Mr Migdal was a promising dancer, and appeared in the BBC show, The Greatest Dancer, as part of the dance troupe, Prospect Fraternity, in 2019.
Mr Migdal was attacked on Cuttys Lane at about 23:20 BST, shortly after he left his Year 13 Prom at Saint John Henry Newman Catholic School, where he was due to take his A-Levels this week.
Hundreds of mourners attended his funeral service on Wednesday, with about 400 more gathering outside on Broadway Gardens as it was live-streamed.
They included school friends, family from the UK, USA and Poland - and representatives from across the UK dance community.
Mass was conducted by auxiliary bishop, Paul McAleenan, with parish priest Fr James Garvey, and nine other members of clergy from across the Stevenage Catholic Deanery.
In a letter, read by Fr Garvey, Cardinal Nichols said he wanted to to assure Mr Migdal's family, friends and parishioners of his "sincere sympathy and prayers at this very difficult time".
"Such a loss in these circumstances leaves us with many questions," the message read.
"I pray as you recall your memories of Kajetan with real thankfulness in your hearts, you will renew your faith in the promises God makes to us in Jesus Christ, that death is not the end of life but the beginning of a new eternal life with God in heaven.
"May you all be filled with hope and courage."
In a statement, Mr Migdal's family said they had been "overwhelmed by the outpouring of support and love for Kajetan".
"It's been humbling to hear from all the people whose lives he touched," they said.
"Without a doubt, he lives on in the hearts and minds of those who knew him and we feel blessed to know he had such an incredible impact in the short time he was with us.
"We cannot describe how great a hole he leaves, and are grateful for the community's support at this time."
An 18-year-old man from Stevenage has been charged with the murder of Mr Migdal.