Repetition
Poetry often makes use of repeated words. Repetition can be used for emphasis or can reinforce or extend the meaning by playing upon the difference connotations or grammatical functions of the repeated words.

The verbs "praise" and "desire" are repeated here in two different grammatical forms: in each pair, the first is active, the second passive. Narcissus is actively praising and desiring his reflection, but is also, ironically, the passive object of that same praise and desire.