In Acts 8:24, Simon, who formerly practiced magic, asked St. Peter, “Pray for me to the Lord, that nothing of what you have said may come upon me.”
Also, the following verses, found in a Catholic Bible, might help:
In 2 Maccabees 15:12-14, dead Onias and dead Jeremiah are descibed as fervently praying for the whole Jewish community.
In Sirach 48:12-16, probably referring to the events of 2 Kings 13:21, Elisha is described as having performed marvelous deeds after his death.
In Daniel 3:86, from King Nebuchadnezzar’s fiery furnace, the three young men sang: “Spirits and souls of the just, bless the Lord; praise and exalt him above all forever.”