Zimbabwe’s first lady says God wants her husband, President Robert Mugabe, to rule the country and is unimpressed by his challengers. Despite his old age, Grace Mugabe said God gave the 91-year-old leader strength so that he could continue holding office, local media reported.

"Just ask yourself why God continues giving a 91-year-old strength to lead the country. Where have you ever seen a 91-year-old who can stand for two hours?" New Zimbabwe  quoted the first lady as saying at a function in Matabeleland north province Thursday.

Grace, 50, also warned those who might want to challenge Mugabe not to forget ousted former vice president Joice Mujuru, advising them to “tamba nevamwe zvakanaka.” Translation: Play safe. Mujuru, Zimbabwe’s first female vice president, was sacked last year amid allegations of corruption and plotting to overthrow Mugabe, though she denied the claims. "This is what destroyed Mujuru. Do not be caught off-side,” Grace said, according to New Zimbabwe.

Robert and Grace Mugabe Zimbabwean President Robert Mugabe (second left), first lady Grace Mugabe (center) and his daughter Bona (right) cut a birthday cake on February 28, 2015 during the celebration of Mugabe's 91st birthday in Victoria Falls. Photo: JEKESAI NJIKIZANA/AFP/Getty Images

The first lady’s remarks came as Mugabe’s ruling Zanu-PF party faces raging factionalism, as members prepare to succeed the longtime leader once he leaves office. Mugabe has ruled Zimbabwe since the southern African country gained independence in 1980.

The Zanu-PF party has already endorsed Mugabe for the 2018 presidential bid, when he will be 94. But infighting has deeply divided the ruling faction seven months after Mujuru and other prominent Zanu-PF members were fired, according to Zimbabwe Independent newspaper.

Grace, who became the new head of the ruling party’s women’s wing last year, said many Zimbabweans think she is a “mental case,” but her words should be taken seriously. “People think I am playing, but I am not,” the state-owned Herald newspaper quoted the first lady as saying on Thursday.