The Midrash, in Judaism is a term given to a genre of rabbinic literature which collects background and supplementary material on the Hebrew Bible (i.e., the Old Testament).
This, says the Midrash,is meant by the words: 'Only take heed to thyself and keep thy soul diligently lest thou forget the words--דברים meaning "words" as well as "things"--which thine eyes have seen, and lest they depart from thy heart all the days of thy life' (Deut. 4. 9). 'The words which thine eyes have seen' means the Written words which can be seen, and 'lest they depart from thy heart' refers to the Oral law, words committed to memory, laid up in the heart.
This, says the Midrash,is meant by the words: 'Only take heed to thyself and keep thy soul diligently lest thou forget the words--דברים meaning "words" as well as "things"--which thine eyes have seen, and lest they depart from thy heart all the days of thy life' (Deut. 4. 9). 'The words which thine eyes have seen' means the Written words which can be seen, and 'lest they depart from thy heart' refers to the Oral law, words committed to memory, laid up in the heart.