Chasidut for Numbers 23:20

Numbers 23,20. “here I have been instructed to bless, ‎since He has blessed I cannot reverse it.” Bileam clearly ‎explains to Balak his inability to alter G’d’s decrees, as he told him ‎before when he said that the difference between man and G’d is ‎that G’d does not lie. On the other hand, although G’d does not ‎reverse Himself, the righteous are able by their prayers to bring ‎about a reversal of decrees harmful for the Jewish people. ‎‎[In other words, man can sometimes accomplish what G’d ‎is prevented from doing by His own initiative. Ed.]‎