Berri hailed Sadr’s efforts for creating unity in the Arab world, saying he saw unity as a solution to the “lurking strife” emerging among the Arab nations at the time.
The Lebanese official also rejected speculations that Musa Sadr, is dead, saying there is still no evidence proving the death.
The Lebanese official made remarks while addressing thousands of supporters of the Amal Movement, the political party which he leads.
The top Lebanese legislator said Lebanon still holds Muammar Gaddafi, Libya's deposed dictator who was killed in 2011, responsible for the fate of Sadr, who founded the Amal Movement in 1974.
Berri also said that the respected Shia cleric was subject to "the worst type of abduction history has known at the hands of Gaddafi."
The Lebanese parliament speaker called on the Lebanese government to give the issue more attention, saying investigation into the case was ongoing.
Berri also noted that a Lebanese team had visited Libya in February to receive further information on the mysterious issue.
Imam Musa Sadr was a highly revered Shia cleric from Iran who came to Lebanon in 1959 to work for the rights of Shia Muslims.
The gathering in the southern port city Tyre was meant to commemorate 38 years since Sadr, his companion, Sheikh Mohammad Yaacoub, and journalist Abbas Badreddine went missing during a trip to Libya.
Since Gaddafi was deposed in 2011, Lebanon and Iran have repeatedly called on the Libyan government to probe Sadr's kidnapping and the related issues.
Hannibal Gaddafi, the son of the Libyan dictator, is currently in custody in Lebanon, facing charges of hiding information regarding Sadr’s case.
It is worthy to mention that Imam Khomeini, the late founder of the Islamic Republic had always been pursuing the case of Sadr, who was kidnapped nearly four decades ago in Libya. Imam was doing follow ups before and after the victory of the Islamic Revolution.
"The problem of Mr. Sadr is a very crucial one and has also dealt a blow on us, but I hope that he will come back soon and continue to undertake the tasks which are Islamic and in the interest of the Shi`ah. We should encourage the Shi`ah. You gentlemen should not be disappointed in his absence. God is with righteousness and supports all. You must encourage the Shi`ah. Avoid disunity. God has promised His assistance. Righteousness is on your side. Inspire hope in the people. Rely on yourself in all affairs."
Imam Khomeini made the remarks in a meeting in Neauphle-le-Chateau attended by the Lebanese delegation pursuing Imam Musa Sadr case of kidnapping in Libya.