Why is the contract of manumission binding upon the master but not unilaterally binding upon the enslaved person for dissolution?

Primary text

The contract of manumission is binding on both parties, yet the enslaved person cannot dissolve it under any circumstance; they only possess the right to declare themselves unable to pay and cease earning. This distinction is justified for two reasons. Firstly, manumission inherently involves emancipation conditional upon a specific event. Whoever attaches a condition to the emancipation of their slave cannot revoke that condition, and the emancipation under that condition must occur. The enslaved person is not obligated to fulfill the condition nor can they be compelled to do so. Secondly, the contract of manumission originates from the enslaved person's desire for freedom, while it affects the master's property rights. Therefore, the contract is binding upon the party who obligated themselves for the benefit of another party, giving the beneficiary (the master) the option concerning it, similar to a guarantor or surety who undertakes an obligation for another.