St Thomas Aquinas considers the Resurrection of Jesus Christ in his treatise on Christology in Part III of the Summa Theoiogica, Q53. In the First Article of Q53, he asks Whether it was necessary for Christ to rise again? Thomas quotes St Luke 24.46 (`Thus it is written, that the Christ should suffer and on the third day rise from the dead’), and offers five reasons why this is so. I summarize them below: they make a sound basis for a series of Easter sermons from Low Sunday to the Sunday before Ascension Day, inclusive. Note how closely St Thomas roots all his reasoning in Scripture.
First, the Resurrection of Christ attests to the Justice of God. God exalts those who humble themselves for his sake (see Luke 1.52). Christ has humbled himself on the Cross, out of love for God, and obedience to him; therefore, God has lifted him up to a glorious Resurrection.
Second, the Resurrection of Christ instructs us and confirms us in our faith. The Resurrection proves Christ’s divinity (2 Corinthians 13.4) and it establishes the sure ground for our belief in him (1 Corinthians 15.14; Psalm 29.10).
Third, the Resurrection of Christ is the grounds for our hope, for where Christ our Head has gone, we too hope to follow (1 Corinthians 15.12; Job 19.25, 27.)