Joseph Alleine preaches about the profound message of the Gospel, inviting all to prepare for the coming of the Lord. He emphasizes the joy of salvation and the blessings that come from a covenant relationship with God, highlighting the peace and mercy that God offers to all who believe. The sermon calls for a heartfelt response to God's invitation, urging listeners to recognize their need for redemption and to embrace the grace that is freely given. Alleine paints a vivid picture of God's love and faithfulness, encouraging the faithful to rejoice in their identity as God's chosen people.