The difference here is the words intercessor and mediator.
A mediator typically in this case means “acting through” while inercession is acting on behalf of someone.
Big difference.
God is acting through Jesus, Saints act (pray) on our behalf. The direction and target of the interaction is reversed.
And a mediator is typically a neutral party who negotiates. An intercessor simply asks on our behalf. We pray for one another every day. Scripture is full of intercessory prayer.
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Then the people came to Moses and said, “We have sinned in complaining against the LORD and you. Pray the LORD to take the serpents from us.” So Moses prayed for the people, and the LORD said to Moses, “Make a saraph and mount it on a pole, and if anyone who has been bitten looks at it, he will recover.” (Numbers 21:7-8)
Now, therefore, take seven bullocks and seven rams, and go to my servant Job, and offer up a holocaust for yourselves; and let my servant Job pray for you; for his prayer I will accept, not to punish you severely. For you have not spoken rightly concerning me, as has my servant Job." Then Eliphaz the Temanite, and Bildad the Shuhite, and Zophar the Naamathite, went and did as the LORD had commanded them. And the LORD accepted the intercession of Job. Also, the LORD restored the prosperity of Job, after he had prayed for his friends; the LORD even gave to Job twice as much as he had before. (Job 42:8-10)*
Intercessory prayer springs from the idea of the Communion of Saints in which we profess faith when we say the creed at Mass. Nowhere does it say in the Bible that the spirits of dead people who make it to heaven are unable to pray for us or that they are somehow prevented from praying for us. In fact, the Bible is rife with examples of spirits praying for us and bringing our peteitions before God.
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I can now tell you that when you, Tobit, and Sarah prayed, it was I who presented and read the record of your prayer before the Glory of the Lord; and I did the same thing when you used to bury the dead. … … I am Raphael, one of the seven angels who enter and serve before the Glory of the Lord." (Tobit 12:12,15)
See that you do not despise one of these little ones, for I say to you that their angels in heaven always look upon the face of my heavenly Father. (Matthew 8:10)
When he took it, the four living creatures and the twenty-four elders fell down before the Lamb. Each of the elders held a harp and gold bowls filled with incense, which are the prayers of the holy ones. (Revelation 5:8)
Another angel came and stood at the altar, holding a gold censer. He was given a great quantity of incense to offer, along with the prayers of all the holy ones, on the gold altar that was before the throne. The smoke of the incense along with the prayers of the holy ones went up before God from the hand of the angel. (Revelation 8:3-4)*
Spirits in Heaven are keenly aware of what goes on down here on earth. Paul wrote of the prophets who were killed (sawed in two, etc) and called them a “Great cloud of witnesses” in Hebrews 12:1.
In just the same way, I tell you, there will be rejoicing among the angels of God over one sinner who repents." (Luke 15:10)
What happens? Do the angels in heaven start rejoicing and the saints look at each other wondering what’s going on? Do the saints say, “There go those crazy angels again, rejoicing over repentant sinners. What a bunch of knuckleads. Now where did I leave my harp?”
And we see a clear example of our prayers for the dead bring not only permitted, but effective and righteous.
But under the tunic of each of the dead they found amulets sacred to the idols of Jamnia, which the law forbids the Jews to wear. So it was clear to all that this was why these men had been slain. They all therefore praised the ways of the Lord, the just judge who brings to light the things that are hidden. Turning to supplication, they prayed that the sinful deed might be fully blotted out. The noble Judas warned the soldiers to keep themselves free from sin, for they had seen with their own eyes what had happened because of the sin of those who had fallen. He then took up a collection among all his soldiers, amounting to two thousand silver drachmas, which he sent to Jerusalem to provide for an expiatory sacrifice. In doing this he acted in a very excellent and noble way, inasmuch as he had the resurrection of the dead in view; for if he were not expecting the fallen to rise again, it would have been useless and foolish to pray for them in death. But if he did this with a view to the splendid reward that awaits those who had gone to rest in godliness, it was a holy and pious thought. Thus he made atonement for the dead that they might be freed from this sin. (2 Maccabees 12:40-46)
We are one community, dead or alive. We are one body of Christ, not two bodies of Christ - one body of Christ who are alive and pray for each other and one body of Christ who are dead and are oblivious to what goes on in the created world.
The only people for whom there is no hope and for whome our prayers and theirs are innefective are those in Hell.
-Tim-