CAUSES OF STAIN
Asajjhaya mala manta anutthana mala ghara
Malam vannassa kosajjam pamado rakkhato rnalam.
Texts not repeated are often soon forgotten;1the house neglected soon decays;
sloth is a blemish on beauty; heedlessness is a blemish on the watchman. 
In Savatthi, people always praised the discourses given by Venerable Sariputta and Maha Moggallana, the two Chief Disciples of the Buddha. On one occasion, Laludayi, on hearing their praises, remarked that the people would also praise him if they were to listen to his discourses. So the people invited Laludayi to deliver a discourse. He went up to the platform but he could not preach the Dhamma. So he requested another bhikkhu to speak first and that he would take the next turn. In this way, he put off having to speak three times.
The devotees lost their patience and reprimanded him, 'You big fool! When we praised the two Chief Disciples you were vainly boasting that you could preach like them. Why don't you preach now?' So Laludayi left the congregation in shame.
When the Buddha was told about the incident, he said, 'Laludayi has learned very little of the Dhamma; he does not recite the religious texts regularly; he has not memorized anything. Whatever little he has learned gets rusty by not being recited.'
- Mantamean religious doctrines, arts and sciences. Non-recitation of the scriptures and non-practice of the arts tend to make one forget them.