Hezbollah chief Hassan Nasrallah, AP
Lebanon's southern border has seen escalating tit-for-tat exchanges, mainly between Israel and Hezbollah, stoking fears of a broader conflict.
The cross-border attacks heated up Thursday, as Israel responded with a "broad assault" after Hezbollah attacked 19 Israeli positions simultaneously.
Rockets also hit the Israeli town of Kiryat Shmona near the border in a barrage claimed by the Lebanese section of Hamas' armed wing.
Iranian Foreign Minister Hossein Amir-Abdollahian has warned that "the region is like a powder keg" and that "anything is possible" if Israel does not stop the war on Gaza.
US President Joe Biden has sent two aircraft carrier groups to the eastern Mediterranean and warned Hezbollah and others to stay out of the conflict.
Lebanese Prime Minister Najib Mikati said he was doing what he could to prevent his country from "entering the war" and warned of an escalation spreading in the "entire region".
Nasrallah's highly anticipated speech will be broadcast as part of an event in Beirut's southern suburbs, at 3:00 pm (13:00 GMT) on Friday, in memory of fighters killed in Israeli bombardments.