Keep on reciting this Qur'an, for by the One in Whose Hand my soul is, the Qur'an slips away from memory faster than camels escaping their tying ropes

The Prophet (may Allah's peace and blessings be upon him) ordered the Companions to recite the Qur'an regularly and not to forget it after they had learned it by heart. He emphasized this fact by swearing that the Qur'an slips away from one's memory faster than camels tied with ropes in the middle of their foreleg. If their shepherd pays attention to them, they remain with him, and if he releases them, they go away and will be lost.