I heard the Messenger of Allah (PBUH) saying:
"When you hear the Adhan, repeat what the Mu'adhdhin says. Then ask Allah to exalt my mention because everyone who does so will receive in return ten rewards from Allah. Then beseech Allah to grant me Al-Wasilah, which is a high rank in Jannah, fitting for only one of Allah's slaves; and I hope that I will be that man. If any one asks Al-Wasilah for me, it becomes incumbent upon me to intercede for him.''
[Muslim]