Abdullah bin Mughaffal reported Allah's Messenger (ﷺ) u saying: 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.
Hadith Referenceصحيح مسلم / کتاب فضائل القرآن وما يتعلق به / 838
This hadith has been narrated by 'Abdullah bin Mughaffal by another chain of transmitters, but with this variation that he (the Holy Prophet) said at the fourth time:" He who wishes (may do to)."
Hadith Referenceصحيح مسلم / کتاب فضائل القرآن وما يتعلق به / 838