And God chanced upon Bilam, and he said to Him: The seven altars I have arranged, and I have offered a bull and a ram on the altar.
Bereishis Rabbah 52:5 / Tanchuma — ויקר as casual, shameful meeting; seven altars vs. the Patriarchs.
English: “And He chanced” — language of the casual, of shame, of impurity of emission; that is, with difficulty and contempt. He revealed Himself by day only to show how dear Israel is. “The seven altars” — he said: Their ancestors built seven, and I alone have arranged against all of them.
Lexical midrash on ויקר and numerical claim against the Patriarchs.
Bilam’s revelation is marked as reluctant and degrading; his boast of seven altars is answered by the fact that the Patriarchs already filled that number.