Numbers 21:17

עלי באר COME UP, WELL from the valley and bring up what you have to bring up! — Whence do we know that it was the well that announced to them these miracles as it is stated above? Because it is said: ומשם בארה “and from there to the well”. For you cannot say that it means: “from that place was (they got) the well”, because was it indeed from there that they got it? Had it not been with them from the beginning of the forty years’ wanderings? But it means that from there it flowed down to the Israelites to proclaim the miracles! Then again, also, the paragraph beginning with the words: אז ישיר … השירה הזאת were spoken at the end of the forty years whilst the well was given them at the beginning of the forty, and what reason then can there be to write it as late as here. But the subject of the song has to be explained in connection with what precedes it (that it was a summons to the well to bring up the bodies of the slain) (Midrash Tanchuma, Chukat 20).

אָ֚ז יָשִׁ֣יר יִשְׂרָאֵ֔ל אֶת־הַשִּׁירָ֖ה הַזֹּ֑את עֲלִ֥י בְאֵ֖ר עֱנוּ־לָֽהּ׃

Then Yisra᾽el sang this song, Spring up, O well; sing to it: