13 “You are the salt of the earth. But if salt loses its flavor, how can it be made salty again? It is no longer good for anything except to be thrown out and trampled on by people! 14 You are the light of the world. A city located on a hill cannot be hidden. 15 People do not light a lamp and put it under a basket but on a lampstand, and it gives light to all in the house. 16 In the same way, let your light shine before people, so that they can see your good deeds and give honor to your Father in heaven.
Sifre Numbers 93Halakhic Midrash
(Bamidbar 11:17) "And I will go down" (veyaradeti): This is one of the ten "yeridoth" written in the Torah. "and I will speak with you": "with you," but not with them. "And I shall increase from the spirit which is upon you, and I will place it upon them.": What was Moses like at that time? Like a lamp placed upon a menorah, from which many lamps are lighted without the first losing any of its light. So, the wisdom of Moses was in no way diminished thereby. "and they will bear with you": What is the intent of this? Because Moses had said (Devarim 1:12) "How can I bear alone your contentiousness, your heresy, and your caviling," he was told "and they will bear with you the burden of the people, and you will not bear it alone."
Notes and References
"... Literal parallels to passages in rabbinic literature are sometimes important for both sources. Thus we read in the Sermon on the Mount ... In the late midrashic compilation, Midrash ha-Gadol, in which ancient midrashic sources have been preserved, we read ... The medieval compilation does not name the midrashim from which its exegetical comments were derived. Quite often early sources can be reconstructed only on the basis of this compilation. The source just cited as a parallel to Matthew may be a tannaitic saying, although this is by no means certain. This striking parallel demonstrates the antiquity of the rabbinic source. It seems that Matthew 5:16b is an elaboration of an earlier Jewish sentence. In the parallel to our verse, Luke 11:33, the lamp metaphor seems to refer to Jesus' ministry. The Christological context in Luke is much closer to the context in the Jewish source, where the lamp metaphor is applied to 'a prophet'; the wording of the saying in Luke, however, has little in common with our midrash. It is plausible, then, that there was a pre-Matthean source whose context was different from the existing redaction of the Sermon on the Mount, but whose wording was similar to the wording in Matthew ..."
Kister, Menahem "Words and Formulae in the Gospels in the Light of Hebrew and Aramaic Sources" in Becker, Hans-Jürgen and Serge Ruzer (eds.) The Sermon on the Mount and its Jewish Setting (pp. 117-147) J. Gabalda, 2005