Yahya related to me from Malik that he had heard that Said ibn al-Musayyab said, "It is said that no-one except a hypocrite leaves the mosque after the call to prayer, except for someone who intends to return".
The Prophet Muhammad ﷺ taught us that we should always strive for sincerity in our actions and words so that we can be true believers of Allah. He warned against being hypocrites who do not follow through with their intentions or commitments as this will lead us away from Allah's path. This hadith reminds us of this important lesson by teaching us not to leave the mosque after hearing the call for prayer unless we intend on returning back soon afterwards.