The president will resume his executive duties on Monday after his return to the country.
The president's spokesperson disclosed this while speaking on Sunrise Daily on Channels TV on Monday.
When the president left the country on May 7 to resume treatment for an undisclosed illness in London, he transmitted his executive powers to Vice President Yemi Osinbajo.
President Buhari returned to Nigeria on Saturday, August 19, to widespread jubilation in Abuja and relief around the country.
While addressing a question on the current status of the president's executive powers, Adesina said a letter will be sent to the National Assembly to inform the legislative arm about the president's return.
He said, "Later this morning that letter will be transmitted and that letter is what signifies his coming back into office. It will be done today.
When notified on the current recess of the National Assembly, he replied, "Transmitting it is what the constitution requires. Once it is sent, he becomes president automatically. They don't have to read it or debate it, No. What the Constitution requires is for him to send it. Once it is sent, he assumes office."
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On Monday morning, during his first national address to the country since his return, President Buhari expressed his happiness at his return, while also urging unity among Nigerians.
He said, "I am very grateful to God and to all Nigerians for their prayers. I am pleased to be back on home soil among my brothers and sisters.
"In the course of my stay in the United Kingdom, I have been kept in daily touch with events at home. Nigerians are robust and lively in discussing their affairs, but I was distressed to notice that some of the comments, especially in the social media have crossed our national red lines by daring to question our collective existence as a nation. This is a step too far.
"Nigeria’s unity is settled and not negotiable. We shall not allow irresponsible elements to start trouble and when things get bad they run away and saddle others with the responsibility of bringing back order, if necessary with their blood.
"Every Nigerian has the right to live and pursue his business anywhere in Nigeria without let or hindrance.
"I believe the very vast majority of Nigerians share this view."