The phrase "treasured possession" refers to something that is extremely valuable and meaningful to someone. It is something that they cherish and hold dear. Full definition
Home is often the most treasured possession of an individual and also the largest financial investments one makes in life. (policybazaar.com)
But ye are a chosen people (Isaiah 43:20; Exodus 6:7), a kingdom of priests, royal priests (Exodus 19:6), a holy nation (Exodus 19:6), a people of treasured possession (Exodus 19:5; Malachi 3:17), for this purpose: that you may declare the wondrous deeds of the One who gave you the calling and summoned you out of darkness into his marvelous light [Isaiah 43:21; 42:12]. (redeeminggod.com)
We only want the best for your children (servicing from newborns to teenagers) and we know they are the most treasured possessions in your life. (palmcove.org)