But asking one person to pray for you in no way violates Christ’s mediatorship, as can be seen from considering the way in which Christ is a mediator. First,
Christ is a unique mediator between man and God because he is the only person who is both God and man. He is the only bridge between the two, the only God-man. But that role as mediator is not compromised in the least by the fact that others intercede for us. Furthermore, Christ is a unique mediator between God and man because he is the mediator of the New Covenant (Heb. 9:15, 12:24), just as Moses was the mediator (Greek
mesitas) of the Old Covenant (Gal. 3:19–20).
The intercession of fellow Christians—which is what the saints in heaven are—also clearly does not interfere with Christ’s unique mediatorship because in the four verses immediately preceding 1 Timothy 2:5, Paul
says that Christians should intercede:
“First of all, then, I urge that supplications, prayers, intercessions, and thanksgivings be made for all men, for kings and all who are in high positions, that we may lead a quiet and peaceable life, godly and respectful in every way. This is good, and pleasing to God our Savior, who desires all men to be saved and to come to the knowledge of the truth” (1 Tim. 2:1–4).
Clearly, then, intercessory prayers offered by Christians on behalf of others is something
“good and pleasing to God,” not something infringing on Christ’s role as mediator.
Why Do Catholics Pray to Saints? | Catholic Answers