After a surprising announcement last week that he would stop cursing, Philippine Pres. Rodrigo Duterte broke his promise Monday and uttered cuss words while speaking in his home town, Davao City.

He warned the police not to be involved in illegal drugs.

“Never enter into illegal drugs. Son of a whore, I will kill you. I’m telling you,” he addressed the police in Filipino, according to Inquirer.

Duterte vowed last week that he would stop cursing because God apparently talked to him and warned him to stop. He was on a flight home from Japan when he heard God’s voice telling him that if he doesn’t stop, “I will bring this plane down now.”

“And I said, who is this? Of course, it's God. So, I promised God not to express slang, cuss words,” he announced in a speech at Davao City International Airport, adding that “a promise to God is a promise to the Filipino people.”

However, he also said in the same speech that there is a time to be foul-mouthed.

“There is always a time, a time to be foul-mouthed,” he said. “I don’t like anybody reading my mind. It’s all calibrated, it’s always timing.”

Duterte’s speeches are known to be peppered with cuss words. He once cursed Pope Francis, whose visit to Manila caused heavy traffic.

On more than one occasion, he spat negative comments to U.S. Pres. Barack Obama after Obama questioned the widespread human rights violations in the Philippine president’s war on drugs.

At one time, he told Obama to “go to hell.” He also challenged American businesses to “pack your bags” if they wish to do so.

On Wednesday, Duterte launched another tirade against the U.S. over the halted sale of 26,000 assault rifles to the Philippines, calling U.S. officials “monkeys.”

“Look at these monkeys, they are stopping the sale of 26,000 assault rifles to us,” he ranted. “Son of a whore. There are a lot of airguns. The Americans are fools.”

The said sale of assault rifles was stopped when American Senator Benjamin Cardin asked to block any sale of such rifles to Philippine police over concerns that these will be used in Duterte’s war on drugs, Rappler reported.

Duterte blamed the U.S. for starting the controversies between the two countries.

He then boasted about China’s openness to sell arms to the Philippines, saying Chinese officials have already given him a brochure.

Duterte also talked about Russia’s willingness to accommodate requests of firearms purchase from the Philippines.

"The Russian ambassador said, 'You come here to Russia. We all have what you want,'" Duterte said.