Thomas Brooks emphasizes the significance of maintaining a sanctified memory filled with precious thoughts of God, as expressed in Psalm 139:17-18. He highlights that the psalmist cherished God's thoughts, valuing them above all else, and encourages Christians to continually enrich their minds with high, noble, and comforting thoughts of God's nature and attributes. A sanctified memory serves as a treasure trove for believers, allowing them to draw strength and solace from their reflections on God's power, wisdom, and compassion.