Definition and Role:
Priestly intercession and mediation refer to the roles and functions of priests as intermediaries between God and His people. In the biblical context, priests are appointed to offer sacrifices, prayers, and supplications on behalf of the people, seeking God's favor, forgiveness, and guidance. This role is foundational in understanding the relationship between God and humanity, as it underscores the need for a mediator due to the holiness of God and the sinfulness of man.

Old Testament Context:
In the Old Testament, the priesthood is established through the line of Aaron, the brother of Moses, as part of the Levitical order. The primary function of the priests was to serve in the Tabernacle (and later the Temple), where they performed sacrifices and rituals as prescribed by the Mosaic Law. The high priest, in particular, held a unique role in intercession, especially on the Day of Atonement (Yom Kippur), when he entered the Holy of Holies to make atonement for the sins of the nation (Leviticus 16).

The priestly intercession is vividly illustrated in the account of Aaron making atonement for the people during a plague (Numbers 16:46-48). Here, Aaron stands "between the dead and the living," highlighting the priest's role as a mediator who intervenes to avert God's wrath.

New Testament Fulfillment:
The New Testament presents Jesus Christ as the ultimate High Priest, fulfilling and surpassing the Old Testament priesthood. The Epistle to the Hebrews elaborates on this theme, emphasizing that Jesus is a priest "in the order of Melchizedek" (Hebrews 5:10), who offers a perfect and eternal sacrifice for sin. Unlike the Levitical priests, who had to offer sacrifices repeatedly, Jesus' sacrifice on the cross was once for all (Hebrews 10:10-12).

Jesus' role as mediator is further affirmed in 1 Timothy 2:5 : "For there is one God and one mediator between God and men, the man Christ Jesus." This underscores the belief that through His death and resurrection, Jesus bridges the gap between God and humanity, providing direct access to the Father.

Theological Implications:
The concept of priestly intercession and mediation has profound theological implications. It highlights the necessity of a mediator in approaching a holy God, reflecting the gravity of sin and the need for atonement. The priestly system in the Old Testament foreshadows the ultimate mediation accomplished by Christ, who not only intercedes for believers but also empowers them to become a "royal priesthood" (1 Peter 2:9), called to offer spiritual sacrifices acceptable to God.

Practical Application:
Believers are encouraged to approach God with confidence, knowing that they have an advocate in Jesus Christ (Hebrews 4:14-16). This assurance transforms the believer's prayer life, worship, and service, as they participate in the priestly calling to intercede for others and proclaim the gospel. The understanding of Christ's mediation fosters a deeper appreciation for the grace and mercy extended to humanity through His sacrificial work.