The second group of two units deals with the compassion that must be shown to other Jews - whether freemen or slaves. Conceptually, both are reflections of the limits God's underlying ownership places on man's. Ideally the slave's relatives, even distant, should show compassion and redeem their brother. If no one redeems the slave, the Torah adds two stipulations. The chapter stresses the unacceptability of a Jew being owned by distinguishing between the dedication of property and self-dedication.
Dedication generally applies to the object actually dedicated.
Although the possibility of redemption generally exists, it is merely an option. What's more, it meets with a penalty - an extra fifth is adas a surcharge. Otherwise, the object remains hekdesh and may be purchased by another. Likewise, the Torah limits the scope of hekdesh's hold on property. God's execution of yetziat mitzraim grants Him ownership of man, and therefore hekdesh's ability to control man is limited.