Hariri arrived in Cairo post his three-day visit to France, where he met President Emmanuel Macron.
President Macron had invited Hariri and his family to France in a bid to defuse tensions in the Middle East.
As per the official Egyptian news agency, Al-Sisi and his Lebanese counterpart Michel Aoun, in a telephonic conversation, underscored "the importance of maintaining Lebanon's stability and the necessity to uphold the Lebanese national interest", reported Turkey's Anadolu news agency.
Hariri announced his resignation as Lebanese prime minister in a televised speech on November 4, shortly after landing in the Saudi capital, Riyadh. He has not returned to Lebanon since then.
The Lebanese President has refused to accept his resignation before he returns.
Hariri's arrival in Cairo coincided with the Egyptian President's arrival from a two-day visit to Cyprus.
He had confirmed his return to Lebanon in the coming days to take part in the Independence Day celebrations.(ANI)