Bala’am was a pious man from  Jerusalem, then called the city of the tyrants. Bal`am knew Allah’s Greatest Name.” `it is also reported, “When Musa and those with him went to the city of the tyrants (Jerusalem), the cousins of Bal`am and his people came to him and said, `Musa is a strong man, and he has many soldiers. If he gains the upper hand over us, we will be destroyed. Therefore, supplicate to Allah that He prevents Musa and those with him from prevailing over us.’ Bal`am said, `If I supplicate to Allah that He turns back Musa and those with him, I will lose in this life and the Hereafter.’ They kept luring him until he supplicated against Musa and his people, and Allah took away what he bestowed on him (of knowledge). Hence Allah’s statement in the Qur’an:

 but he threw them away, so Shaytan followed him up).”‘

 And had We willed, We would surely have elevated him therewith, but he clung to the earth and followed his own vain desires.)

This is the version of the story given by Ibn `Abbas and reported by Ali bin Abi Talhah. Click for Detail

According to another versi, Bala’m and his friends were defeated. Bala’m became furious at the defeat disrespecting the Divine Will. Therefore, in jealousy and revenge,  he started luring the Bani Israel (Moses’) Army to indulge in adultery. One of the senior commanders committed adultery, the rest followed him. Resultantly, Allah punished them with a plague which had killed thousands of people in the region. Bala’m, himself, met a very bad end. He had lost consciousness, and he would roam like a mad and crazy person on the streets of the town, panting and his tongue being hung out of his mouth like a dog.