Q: What should a person do when he enters the masjid while the adhaan is being called out? Should he sit and wait, or should he start praying Tahiyaat al Masjid, or should he wait standing until the adhaan has finished and then start superagatory prayer?
A: It is permissible to sit or remain standing during the Adhaan if one came into the Masjid while the Adhaan is being called out. It is not necessary or Sunnah to remain standing nor is there any special significance or special reward for remaining standing.
Allah Ta'aala knows best
Mufti Siraj Desai