Chapter 25 covers the Sabbatic Year and Jubilee. The sabbath of days was extended to a sabbath of years. Every seventh year was to be a year of rest for the land (verse 5). This was to restore the soil and provide for the poor from what grew from the untilled fields (verse 6). However, it was primarily a recognition of God's sovereignty over the land which He was to give them. Failure to observe the Lord's supremacy resulted in captivity in a foreign land.
The Year of Jubilee is covered in verses 8-55. The cycle of seven sabbatic years was followed by the fiftieth year (verse 8), ushered in by the blowing of the jubilee trumpet on the Day of Atonement (verse 9). This portrays Israel's entrance into the blessings of the Messianic reign, with the Lord in the midst of His people. It means much more than the promised blessings to Israel. It also foreshadows the blessings of Romans 8:19-23 for the entire earth.
Chapter 26 gives the condition of blessing in the land. The blessings for obedience are covered in verses 1-13. To receive blessing, God's people had to be holy and maintain a holy reverence for Him, according to the first table of the Law given at Sinai. The curse of disobedience (verses 14-39) culminated in the captivity of Jerusalem and dispersion of the people among the nations. This prediction and its fulfillment in Jewish history contain powerful evidence for the divine inspiration of the Bible.
This same God, who was rich in mercy toward the children of Israel, is the God we serve today. He loves us and gave His Son to die for us. However, when His children are disobedient, this same merciful, but just, God must chastise them. It would be well for us to turn to Hebrews 12:1-15 and read of God's chastening of those who are His own.