Midrash su Numeri 9:19

And the Lord went before them by day (Exod. 13:21). You find that there were seven clouds of glory in all. And the Lord went before them by day in a pillar of cloud (ibid.) was the first; and Thy cloud standeth over them (Num. 14:14) was the second; In a pillar of cloud (ibid.) was the third; That the cloud tarried (Num. 9:22), the fourth; And the going up of the cloud (Exod. 40:36), the fifth; And whenever the cloud was taken up (ibid., 37), the sixth; and For the cloud of the Lord was upon the Tabernacle (ibid., v. 38) was the seventh. Four of the clouds were at each of the four sides; one was above them, another below them, and the seventh cloud preceded them. The last of the clouds lowered the high places, raised the low places, burnt the serpents and the scorpions, and sprinkled the road (to lay the dust) before them.

(Ibid. 21) "And the L rd went before them by day with a pillar of cloud": We find there to have been seven clouds: here, (Numbers 14:14) twice, (Ibid. 9:19), (Exodus 40:36), (Ibid. 37), (Ibid. 38) —

(Bamidbar 10:34) "And the cloud of the L-rd was above them by day": From here they said: There are seven "clouds": (Bamidbar 14:14) "and in a pillar of cloud You go before them by day," (Shemot 14:19) "and the pillar of cloud turned from before them," (Bamidbar, 14:14) "and Your cloud stands over them," (Devarim 1:33) "and in cloud by day," (Bamidbar 9:19) "And when the cloud lingered over the mishkan," (Shemot 40:38) "For the cloud of the L-rd was on the mishkan by day," (Bamidbar 10:34) "And the cloud of the L-rd was above them by day." There were seven clouds — four on their four sides, one above, one below (to cushion their feet), and one before them, which lowered what was high and raised what was low, and killed the serpents and the scorpions, and swept and sprinkled before them. R. Yehudah says: There were thirteen (clouds) — two on each side, two above and two below, and one before them. R. Yoshiyah says: Four. Rebbi says: Two.