Al-'Allaamah ibn Baaz rahimahullaah said:

“No one leaves off repeating after the mu'adhin except one who is deprived [of good]. Repeating after the mu'adhin carries four great virtues: 1⃣. Forgiveness of sins 2⃣. Admittance into Jannah 3⃣. Prosperity through his intercession ﷺ 4⃣. Supplication being answered after it.“ Ibn Juraij rahimahullah said: “The Salaf would remain silent for the mu'adhin [at the time of calling the Adhan] as they would remain silent for the Qurʿān.” [Fat-hul Baari 2/92]