Numbers 21:16

ומשם בארה AND FROM THENCE TO THE WELL — from there the flow of blood ran to the well. How? The Holy One, blessed be He, said: Who will inform my children of those miracles? — The proverb says: If you have given bread to a child let its mother know (i.e., since the mother has, to an extent, benefitted by this, and the child cannot tell her, you should do so) (Shabbat 10b). After they (the Israelites) had passed by, the mountains returned to their original positions, and the well that followed the Israelites flowed down into the valley and brought up from there the blood and the arms and other limbs of those who had been thus killed, and carried them around the camp, so that Israel saw them, and they sang a song of triumph, as follows (Midrash Tanchuma, Chukat 20):

וּמִשָּׁ֖ם בְּאֵ֑רָה הִ֣וא הַבְּאֵ֗ר אֲשֶׁ֨ר אָמַ֤ר יְהֹוָה֙ לְמֹשֶׁ֔ה אֱסֹף֙ אֶת־הָעָ֔ם וְאֶתְּנָ֥ה לָהֶ֖ם מָֽיִם׃ {ס}        

And from thence they went to Be᾽er: that is the well of which the Lord spoke to Moshe, Gather the people together, and I will give them water.