In April 1981, a young Islamic cleric marked the starting line for his ascent in Malaysian politics with fiery sermons.

Mr Abdul Hadi Awang's most memorable words from one sermon were that Muslims cannot work with nationalist Malay party Umno because it "retains the Constitution of the (British) colonialists, the laws of the infidels". Known as Amanat Haji Hadi, or Haji Hadi's Edict, his widely cited view deeply split Malay Muslims for decades.

The edict had its supporters and detractors, and the division caused people to pray in different mosques, be buried in separate cemeteries, and even divorce their spouses. The backdrop to Malaysia's lurch towards Islamic fundamentalism then was the aftermath of the 1979 Iranian revolution, and the Soviet invasion of Afghanistan in the same year, both causing a sea change in the Muslim world.

Today, 36 years later, Datuk Seri Hadi espouses quite the opposite view. Muslims are allowed to work with Umno now, even though the ruling party has not changed the Constitution and only selectively injects Islam into its policies.

"Malay political power lies with PAS (Parti Islam SeMalaysia) and Umno. PAS is open to (working with) any party but it has to accept Islam," Mr Hadi said, giving his rationale for closer ties with Umno last month.

The path of that fiery young man in the 1980s - a graduate of Saudi Arabia's Islamic University of Madinah and Egypt's Al-Azhar University - has taken many twists and turns before reaching its current destination.

Mr Hadi, 69, is today president of the country's second-biggest political party by membership, a tuan guru (master teacher) to more than 800,000 PAS members and an aspiring prime minister. Only Umno, with 3.2 million members, is bigger.

Old pictures of him show a trim young man with a long black beard and white robes. These days, he still dons similar robes but has a spare tyre and his beard is mostly grey.

And, while his speeches remain fiery, there is an added mellowness to them, as befits a seasoned politician. It is not all hellfire and brimstone - this Member of Parliament now speaks about people burdened with high inflation and affirming the rights of non-Muslims under PAS rule.

"He has strong leadership skills and is knowledgeable. He has the talent to become prime minister," enthused Mr Daud Haron, 66, a palm-oil smallholder from Johor on the sidelines of the party's annual congress in Kedah.

The five-day congress that ends today is Mr Hadi's best yet. The Terengganu-born cleric, the son of an Islamic preacher, was unchallenged at the biennial party polls and is into his 15th year as PAS president, a record.

Mr Hadi has two wives and 14 children, with eldest son Muhammad Khalil, 40, recently elected chief of PAS Youth.

Mr Hadi was not active only in PAS. He was also active in the 1980s in the Malaysian Muslim Youth Movement, ABIM - that era's premier Islamic organisation for activists that shaped the early thinking of current local Islamists.

PAS under Mr Hadi in 2008 formed an alliance with opposition parties Parti Keadilan Rakyat (PKR) and Chinese-based Democratic Action Party (DAP). PKR is led by Anwar Ibrahim, who was ABIM president in the 1980s.

PAS, during its alliance with PKR and the DAP that lasted nearly eight years, affirmed that it will abide by the current Constitution.

But, in 2015, after the death of revered PAS spiritual leader Nik Aziz Nik Mat and with Anwar in jail, Mr Hadi U-turned back to his fundamentalist roots.

"It is true that Hadi has changed. In one sense, you could say that he has mellowed," said Mr Yang Razali Kassim, senior fellow at the S. Rajaratnam School of International Studies. "Yet, in another sense, he is becoming more conservative."

Mr Hadi has found that today's Umno has ready ears for his Islamic agenda, though sceptics say Prime Minister Najib Razak wants only to burnish Umno's Islamic credentials.

Umno last month helped PAS raise the issue of Islamic penal code amendments in Parliament.

Mr Hadi's next big quest is to deliver on his ambitious promise that the party would win 40 Parliament seats and five states at the next general election.

When asked on Saturday whether the targets are achievable, he said: "We are a party that lives in the realm of reality."