Ch. 22, v. 22: "Va'yichar af Elokim ki holeich hu" - Why was Hashem angered by Bilom's going, since He said to Bilom "kum leich itom" (verse 20)? The Chid"o in Nachal K'dumim answers with the gemara mentioned earlier, that Bilom wanted to ch"v curse the bnei Yisroel at the exact moment of Hashem's daily anger. The gemara says that since Bilom planned to do this Hashem refrained from being angry during those days, contrary to His regular practice. However, once Bilom took to the road and made his way to Moav, Hashem returned to His daily "anger for a fleeting moment." Since Bilom was travelling he didn't have the presence of mind to calculate the exact moment. This is the meaning of our verse. Hashem was willing to be angry, as is His daily practice of "V'Keil zo'eim b'chol yom" (T'hilim 7:12) because Bilom was travelling.

Taken from Sedrah Selections - Balak