Praise be to Allah, The Lord (The One and Only) of the Worlds, and blessings and peace be upon our Master Muhammad, the Truthful and the Faithful.

Good manners are what man leaves behind after his death. Furthermore, Allah the Almighty has made the Prophet (PBUH) distinguished with many noble traits, but when He commends him, He the Almighty says:

(And verily, you (O Muhammad, PBUH) are on an exalted standard of character.)

[Al- Qalam, 4]

Allah the Almighty does not say to His Prophet PBUH: You have great morals, but what does "You have great morals" mean? To explain its meaning, let me give you this example: You have some fruit, and upon welcoming some high-ranking visitors who come from a far place, you become hesitant whether to keep the fruit to your children or to offer it to your visitors. If you finally decide to bring the fruit to the guests, you are a man who has great morals; however, if you offer the fruit to visitors without any hesitation or inner conflict with yourself, then you are a man on an exalted standard of character. Accordingly, making a decision to do good things without hesitation or inner conflict means you are "on an exalted standard of character." 

Bear in mind, the things that are left behind after one's death are good manners.