There Is between the two calls (Adhan and Iqama) a prayer. And he mentioned it three times, and at the third time he said: This applies to those who wish to do it.
Sahih Muslim Book 6, Hadith 368
← Previous Hadith When we were in Medina, the moment the Mu'adhdhin made the call to the sunset prayer, the people hastened to the pillars of the mosque and prayed two rak'ahs with the result that any stranger coming into the mosque would think that the obligatory prayer had been observed owing to the number who were praying then.

Sahih Muslim Book 6, Hadith 367 Next Hadith → " He who wishes (may do to)."

Sahih Muslim Book 6, Hadith 369