A loved one dies, a mother, a father, a daughter, or a son. We do not know what fate awaits them after death, so we want to help them. This is where the dilemma arises: can we pray for this person?
Notice, reader, that we do not ask the question: can we pray TO the deceased person.
Why?
Because the Bible informs us that we can only pray to the Father and the Son. We are NOT allowed to pray to any other person. Similarly, we are not allowed to call up the souls of deceased people, talk to them. God forbids this.
Let’s analyze a few verses and see what God says about praying FOR the deceased.

1 – Description of prayer (and sacrifice) for the deceased:

„For if he had not believed that the resurrection belongs to those who have fallen in war, it would have been superfluous and foolish to pray for the dead. … [Juda/Judah] made atonement for the dead, that they might be delivered from their sin.” – 2 Maccabees 12:44-45.

Juda/Judah Maccabeus’ soldiers find amulets dedicated to gods on the dead, which was a sin according to Mosaic Law. The gathered faithful pray to God, asking for forgiveness for the dead, and then make an atonement sacrifice on their behalf.

2 – Immersion for the dead:

“Otherwise, what will they do who are immersed on behalf(5228) of the dead? If the dead are not raised at all, why are they immersed on behalf(5228) of the dead? Why do we also expose ourselves every hour?” – 1 Corinthians 15:29-30.

Paul mentions the practice of “immersing for the dead” in Corinthians. He does not judge whether it is right or wrong. This example shows that in the first century there was a belief that the living could help the dead.

https://jesu.pl/immersion-for-the-dead/

3 – Onesiphorus was probably already dead:

„The Lord show mercy to the house of Onesiphorus, because he often refreshed me, and was not ashamed of my chains, but when he was at Rome he diligently sought me out and found me. The Lord grant him that he may find mercy of the Lord that day. And You know very well how many services he did me at Ephesus.” – 2 Timothy 1:16-18

Paul asks the Lord to find mercy for Onesiphorus. He recalls his beautiful actions.

4 – Christ’s prayer for the deceased:

„So they took away the stone. And Yeshu lifted up His eyes and said, 'Father, I thank You that You have heard Me. I know that You always hear Me. But I said this because of the crowd standing by, that they might believe that You have sent Me. And when He had said this, He cried out with a loud voice, ’Lazarus, come out!’ And the dead man came out…” – John 11:41-44.

Here we also have the prayer of the Apostle Peter for the deceased: Acts 9:36-42.

5 – After the death of the body, the character continues to live:

“It is appointed for men to die once, but after this the judgment.” – Hebrews 9:27.

6 – The dead are not conscious:

“…for the living know that they will die, but the dead know nothing… They have no part in anything that happens under the sun” – Ecclesiastes 9:5-6.

7 – The Good News can be proclaimed to the deceased:

„They will give account to Him who is ready to judge the living and the dead(3498). For also the dead(3498) has the Good News been preached, that they may be judged according to the flesh of men, but live according to God in the spirit(4151)” – 1 Peter 4:6.

8 – The souls of the murdered pray for justice:

“When he had opened the fifth seal, I saw beneath the altar the souls of those who had been slain for the Word of God and for the testimony they held.
And they cried with a loud voice, saying, ‘When, O Lord, holy and true, will you begin to judge and avenge our blood on those who dwell on the earth?’
And there was given to each of them a white robe, and it was said to them that they should rest for a little while longer, until the number of their fellow servants and their brethren who were to be killed even as they had been, was completed.” – Revelation 6:9-11

https://jesu.pl/is-the-good-news-preached-to-the-dead/

Let’s summarize the selected verses

We have examples in the Bible where people prayed for the dead, immersed themselves for the dead, Christ prayed to God for a dead person in order to raise them up.
Many people will say: „Why pray for a dead person if they are going to sheol or heaven? Now they are in God’s hands and will be judged, so our prayers are useless.”
There is an interesting verse that informs us: „The fervent prayer of a righteous person avails much” – James 5:16b. The whole of verse 16 encourages confessing sins to one another and praying for one another. However, this part of the verse „The fervent prayer of a righteous person avails much” can be applied to other things.
The Bible informs us not to fall into deep mourning:

“We do not want you to be in uncertainty, brothers, about those who have fallen asleep/died, so that you will not grieve as others do when they have no hope. For if we believe that Yeshu died and rose again, even so God will bring with Him those who have fallen asleep in Yeshu.” – 1 Thessalonians 4:13-14

https://jesu.pl/what-happens-to-our-loved-ones-when-they-die/

Putting all these verses together, we can come to at least two conclusions:
1 – someone will say: „I leave the deceased person in God’s hands. I can’t help them anymore. A just court will judge their life.”
2 – someone else will say: „I know that God will judge the deceased person justly, but I want to remember in prayer how beautifully they helped people, how beautifully they loved people.”
The most difficult situation will be when the deceased person was far from God, had no love…

„And I heard a voice from heaven saying, Write, Blessed are the dead which die in the Lord from now on. Amen, saith the Spirit; they shall rest from their labors (works), for their works follow them.” – Revelation 14:13.