President Muhammadu Buhari returned to London on May 7 for medical follow-up.
He had earlier spent 49 days in the British capital to treat an undisclosed ailment.
Mrs Buhari joined the President in London five days ago.
She spoke in Abuja through her senior special assistant on administration, Hajo Sani, at the 23rd annual Ramadan lecture of Ansar-ud-deen Society of Nigeria (ADS).
“My husband is recovering very fast. And very soon, he will return to the country to resume his official duties”, she was quoted as saying.
“I thank Nigerians for their prayers for my husband. Please, do not relent in your prayers.”
The message was said to have sparked shouts of Allahu Akbar! Allahu Akbar!! Allahu Akbar!!!(God is great) by the Muslim faithful.
Mrs Buhari added: “The President will be back very soon.”
She said she is “hopeful of observing this year’s Eid-el-Kabir festival at the ADS Mosque in Maitama as she had been doing even before getting into office.”