Dear SHoJ,
since others have already done a good job in answering your question, I thought I might offer you some useful Bible passages to show to people who object to the communion of saints / intercessory prayer of saints:
Hebrews 12:1 “says we “are surrounded by so great a cloud of witnesses” after speaking at length of saints that have died.
In Mark 9:4, Jesus has a conversation with Moses and Elijah (both of whom had long since died) on the Mount of Transfiguration.
Revelation 5:8 describes humans in heaven offering the prayers of those on earth to God: “the twenty-four elders fell down before the Lamb, each holding a harp, and with golden bowls full of incense, which are the prayers of the saints”
In Revelation 6:9-10, the souls of martyrs in heaven cry out to God for earthly justice.
James 5:16 says that “The prayer of a righteous man has great power in its effects.” [This is why so many miracles happen through the intercession of saints.]
Tobit 12:12,15: “And so, when you and your daughter-in-law Sarah prayed, I brought a reminder of your prayer before the Holy One; and when you buried the dead, I was likewise present with you…I am Raphael, one of the seven holy angels who present the prayers of the saints and enter into the presence of the glory of the Holy One.”
Baruch 3:4: ”O Lord Almighty, God of Israel, hear now the prayer of the dead of Israel and of the sons of those who sinned before thee, who did not heed the voice of the Lord their God, so that calamities have clung to us.”
2 Maccabbees 15:12-16 describes a vision in which two departed saints continue pray for and strengthen the people of Israel:
“What he saw was this: Onias, who had been high priest, a noble and good man, of modest bearing and gentle manner, one who spoke fittingly and had been trained from childhood in all that belongs to excellence, was praying with outstretched hands for the whole body of the Jews. Then likewise a man appeared, distinguished by his gray hair and dignity, and of marvelous majesty and authority. And Onias spoke, saying, “This is a man who loves the brethren and prays much for the people and the holy city, Jeremiah, the prophet of God.” Jeremiah stretched out his right hand and gave to Judas a golden sword, and as he gave it he addressed him thus: “Take this holy sword, a gift from God, with which you will strike down your adversaries.”
Oftentimes, people who object to these practices believe in using “scripture alone” even though the Bible doesn’t teach 'scripture alone." That is why I listed only Bible verses, to reach out to those people. I hope this is helpful.