Reciting only the verses that one knows?

Firstly: 

Reading Qur’aan 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 virtue of that, such as the words of the Prophet (peace and blessings of Allaah be upon him): “Read the Qur’aan, for it will come on the Day of Resurrection interceding for its companions.” Narrated by Muslim (804) and by al-Bukhaari in a mu’allaq text. 

It was narrated that ‘Abd-Allaah ibn Mas’ood said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever reads one letter of the Book of Allaah will have one hasanah for it, and each hasanah is a tenfold reward. I do not say that alif-laam-meem is a letter, rather alif is a letter, laam is a letter and meem is a letter.” Narrated by al-Tirmidhi (2910) who aid: it is hasan saheeh. Classed as saheeh by al-Albaani in Saheeh al-Tirmidhi. 

Secondly: 

It is permissible for a person to recite whatever he can of what he knows of the Qur’aan –according to his ability. 

It was narrated from ‘Aa’ishah (may Allaah be pleased with her) that the Prophet (peace and blessings of Allaah be upon him) said: “The one who recites the Qur’aan and learns it by heart, will be with the noble righteous scribes (in Heaven) and the one who exerts himself to learn the Qur’aan by heart and recites it with great difficulty, will have a double reward.” Narrated by al-Bukhaari (4937). 

The hadeeth indicates that the one who finds it difficult to read Qur’aan will be rewarded for his reading. This is all aimed at encouraging one to read Qur’aan and not to forsake the Qur’aan. 

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 Mus-haf so as to attain the reward for reciting, so that he may combine the two: memorization and recitation. 

We ask Allaah to help us and you to memorize His Book and to read it during some hours of the night, and at the ends of the day (cf. Ta-Ha 20:130), for He is Able to do that. 

And Allaah knows best.