فَسَبِّحْ بِحَمْدِ رَبِّكَ
Then glorify your Lord with praise. (110:3)
The bāʾ of bi-ḥamd has recognized explanations connected with accompaniment or association; the basic point is that glorification is to be joined with praise. The iḍāfah rabbika addresses the Prophet in relation to the Lord whose support has just been described.
Combining declaring divine transcendence with praising divine excellence makes the expression richer than treating tasbīḥ and ḥamd as identical synonyms.