What is the biblical reason Catholics pray to dead saints for intercession?
No one prays to dead saints, because those in heaven are more alive than we are. The Lord is God of the living, not of the dead. The fervent prayer of a righteous man is very powerful (Jas 5:16). Those in heaven are surely righteous, since nothing unclean can enter heaven (Rv 21:27). Those in heaven are part of the Mystical Body of Christ and have not been separated from us by death, but surround us as a great cloud of witnesses (Heb 12:1). They stand before the throne of God and offer our prayers to him (Rv 5:8) and cheer us on as we run the good race. Intercession among members of the body of Christ is pleasing to God (1 Tm 2:1-4) and even commanded by him (Jn 15:17). Those in heaven have a perfected love, so how could theynot intercede for us? Christ is the vine, and we are the branches; if we are connected to him, we are inseparably bound together as well. Can the eye say to the hand, “I need you not”? Neither are we to say we don’t need the prayers of our brothers and sisters (alive here or in heaven), because salvation is a family affair.