The Virgin Mary and the rest of the Saints being sinners, could not satisfy so much as for them selves.
Related quotations
It may be added also that the doctrine of the Papists that the saints or the Virgin Mary may act as mediators to procure blessings for us, is false. There is but "one Mediator;" and but one is necessary. Prayer offered to the "saints," or to the "Virgin," is idolatry, and at the same time removes the one great Mediator from the office which he alone holds, of making intercession with God.
However, we cannot in any way acknowledge or accept what our opponents openly say, namely that Mary is to be invoked as a mediator between God and humans, or that she is our patron and advocate. We do not believe that this is either a tradition of Holy Scripture or a command from God. We believe that God, who alone grants all salvation for the present and future, is the one to be invoked alone. We believe that Christ alone [since He alone is true God and true man] is the true mediator between God and humans. We believe that He, who alone can satisfy all humans, is the patron and advocate with the Father.
It is with great propriety, in speaking of the joy of her heart, that she gives to God the appellation of Savior. Till God has been recognised as a Savior, the minds of men are not free to indulge in true and full joy, but will remain in doubt and anxiety.
But can she not furthermore be venerated as a mediator and intercessor between God and us with the honour of invocation? Answer: No, since no one should be invoked except God alone in Christ, our only Mediator, Saviour, and Intercessor