Imaam Maalik (rahimahullah) replied, “Bring the kitaabs which these ‘Ulamaa have prepared to me.” When the kitaabs were brought, Imaam Maalik (rahimahullah) looked through them and then placed them aside. He thereafter remarked, “Remember that only that work will gain acceptance by Allah Ta‘ala which was done solely for His pleasure.”
On account of the sincerity of Imaam Maalik (rahimahullah), Allah Ta‘ala blessed his kitaab with acceptance. Hence, it was his kitaab that stood the test of time, whereas many of the other kitaabs written were forgotten and lost.
(Tazyeen-ul-Mamaalik pg. 92)