Narrated by 'Umar ibn al-Khattab (RA), he said, The Messenger of Allah (ﷺ) said: When the muazzin says "Allahu Akbar Allahu Akbar", Then if any of you say “Allahu Akbar Allahu Akbar; When the muazzin says "Ashhadu an laa ilaaha illallah", If he says "Ashhadu an laa ilaaha illallah"; When Muazzin says “Ashhadu Anna Muhammadar Rasoolullah, If he says "Ashhadu Anna Muhammadar Rasoolullah"; When the muazzin says "Haiya alas salah", If he says "Laa hawla wala quwwata illa billah"; When the muazzin says "Haiya alal falah", If he says "Laa hawla wala quwwata illa billah"; When the muazzin says "Allahu Akbar Allahu Akbar", If he says "Allahu Akbar Allahu Akbar", Then when the muazzin says "Laa ilaaha illallah", If he says "Laa ilaaha illallah" If he says these things from the heart, then he will go to Paradise.

Reference: Muslim: 385