If you’re looking for an excellent intro and overview of the Feasts of the Lord in the Old Testament, the following links from Jesus Plus Nothing! are highly recommended!
The feasts of the Lord – An introduction and overview
The Spring Feasts – Jesus’ First Coming
The Sacrifice – Jesus in the feast of Passover
The Burial – Jesus in the feast of Unleavened Bread
The Resurrection – Jesus in the feast of Firstfruits
The Comforter – Holy Spirit in the feast of Pentecost