i.e., if I?m in the 1st Rakaat, when do I stop, and so on?
If a person has already commenced with the Sunnat-e-Muakkadah of Dhuhr and
the Jamaat commences, then he should make Salaam after two Rakaats and join
the Jamaat. And if he already commenced with the third Rakaat, then it is
necessary to complete the full four Rakaats. (Bahishti Zewar vol.2 pg.170)
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai