سَيِّدُكَ يَأْمُرُكَ بِكَذَا
Your master commands you to do this.
When the speaker’s identity is already understood, a pronoun might be expected. Using “سَيِّدُكَ” instead foregrounds the speaker’s authority and the duty of obedience.
An explicit noun is not universally better than a pronoun; its rhetorical justification lies in the specific relationship or description that it makes salient.