“Midrash is normally composed out of already-existing material, accepted as authoritative because it comes from the Scripture or the tradition. Using this raw material, the new is evolved. Naturally new terms, new phrases, new symbols and new ideas are introduced but the greater part is taken from that which already exists in the authoritative tradition. Midrash starts from a text, a phrase or often a single word; but the text is not simply explained–its meaning is extended and its implications drawn out with the help of every possible association of ideas.”
Birger Gerhardsson. The Testing of God’s Son (Matthew 4:1-11 and PAR.): An Analysis of an Early Christian Midrash. Lund: Gleerup, 1966, 14.