In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
It is permissible for a person to recite whatever he can of what he knows of the Quran according to his ability.
Answering your question, the Fatwa Center at Islam Q and A, states:
Reading the Quran is one of the greatest of good deeds and acts of worship for which a Muslim will be rewarded. There are many texts which speak of the virtues of reciting the Quran. The Prophet (peace be upon him): “Read the Quran, for it will come on the Day of Resurrection interceding for its companions.” (Muslim and Al-Bukhari)
It was narrated that Abdullah ibn Masud said: The Messenger of Allah said: “Whoever reads one letter of the Book of Allah will have one hasanah for it, and each hasanah is a tenfold reward. I do not say that alif-lam-meem is a letter, rather alif is a letter, lam is a letter and meem is a letter.” (At-Tirmidhi)
It is permissible for a person to recite whatever he can of what he knows of the Quran –according to his ability.
It was narrated from Aishah (may Allah be pleased with her) that the said: “The one who recites the Quran and learns it by heart, will be with the noble righteous scribes (in Heaven) and the one who exerts himself to learn the Quran by heart and recites it with great difficulty, will have a double reward.” (Al-Bukhari)
The hadith indicates that the one who finds it difficult to read Quran will be rewarded for his reading. This is all aimed at encouraging one to read the Quran and not to forsake the Quran.
So there is nothing wrong with a person reciting the verses that he knows, whether it is three verses or more or less.
If he can read but he has only memorized a few verses, then he is advised to devote some of his time for memorization and some for reading from the mushaf so as to attain the reward for reciting, so that he may combine the two: memorization and recitation.
Almighty Allah knows best.