Sami ul Haq was known as the spiritual father of Taliban.
Haq ran an Islamic seminary in the north-western Pakistani town of Noshera and was a teacher to most of the Afghan Taliban's leaders, including the militia's founding father, Mullah Omer, said Taliban spokesman Yousaf Shah.
Ul-Haq was in 2014 a member of the negotiating committee from the Pakistan homegrown Tehreek-e-Taliban Pakistan (TTP) - who brokered a ceasefire with the government, although the talks later failed.
"He was stabbed multiple times", Maulana Hamid said.
The Senate website describes him as: "A qualified religious scholar, an educationist, a research scholar and a lieutenant of his father, late Maulana Abdul Haq".
Condolences started pouring in after religious scholar and Jamiat Ulema-e-Islam-Sami (JUI-S) chief Maulana Samiul Haq was assassinated in a targeted attack in Rawalpindi on Friday.
In a statement, the prime minister directed the authorities concerned to investigate the incident and bring the perpetrators to justice.
The funeral prayers of Maulana Sami-ul-Haq will be offered at Darul Uloom Haqqania Akora Khattak at 2 pm tomorrow.
Prime Minister Imran Khan strongly condemned the martyrdom of Maulana Samiul Haq.
JUI-S's Peshawar president also confirmed Haq's death following an assassination attempt in Rawalpindi. Former prime minister Nawaz Sharif condemned the martyrdom of Maulana Sami and expressed huge grief over it.
Minister of State for Interior Shehryar Afridi has also condemned the assassination.
No individual or group has so far claimed responsibility behind the assassination of Maulana Samiul Haq. Khan had been criticized for supporting Haq, including donating funds to the Haqqania seminary when he was head of a provincial government.