The rally will be Modi's first-ever in Bihar after the one at Gandhi maidan in Patna, where multiple blast had occured.
BJP and LJP had formed an ally last week. The'hunkar' rally today will be held next to a ground at Bakhri-Parimasa area on the Darbhanga-Muzaffarpur national highway.
On Thursday, BJP President Rajnath Singh informed that Paswan would meet Modi over the next few days after their parties formalised a pre-poll alliance ahead of the general elections, due by May.
Earlier, Paswan had severely criticised Modi for the communal riots that ravaged his state in 2002, leading to his walkout from the BJP-led National Democratic Alliance (NDA).