The sin of the person who recites the Qur'an to show off or to gain some worldly benefit, or to feel proud etc.

English translation

Narrated `Ali:

I heard the Prophet (ﷺ) saying, "In the last days (of the world) there will appear young people with foolish thoughts and ideas. They will give good talks, but they will go out of Islam as an arrow goes out of its game, their faith will not exceed their throats. So, wherever you find them, kill them, for there will be a reward for their killers on the Day of Resurrection."

English translation

Narrated Abu Sa`id Al-Khudri:

I heard Allah's Messenger (ﷺ) saying, "There will appear some people among you whose prayer will make you look down upon yours, and whose fasting will make you look down upon yours, but they will recite the Qur'an which will not exceed their throats (they will not act on it) and they will go out of Islam as an arrow goes out through the game whereupon the archer would examine the arrowhead but see nothing, and look at the unfeathered arrow but see nothing, and look at the arrow feathers but see nothing, and finally he suspects to find something in the lower part of the arrow."

English translation

Narrated Abu Musa:

The Prophet (ﷺ) said, "The example of a believer who recites the Qur'an and acts on it, like a citron which tastes nice and smells nice. And the example of a believer who does not recite the Qur'an but acts on it, is like a date which tastes good but has no smell. And the example of a hypocrite who recites the Qur'an is like a Raihana (sweet basil) which smells good but tastes bitter And the example of a hypocrite who does not recite the Qur'an is like a colocynth which tastes bitter and has a bad smell."