Srimad-Bhagavatam: Canto 8 - Chapter 1 - Verse 23


भवद्भ‍िर्निर्जिता ह्येते बहुशोऽनुचरा हरे: ।दैवेनर्द्धैस्त एवाद्य युधि जित्वा नदन्ति न: ॥ २३ ॥


bhavadbhir nirjitā hy etebahuśo ’nucarā hareḥdaivenarddhais ta evādyayudhi jitvā nadanti naḥ


Previously, being empowered by providence, you defeated a great number of such followers of Lord Viṣṇu. But today those same followers, having defeated us, are roaring in jubilation like lions.


Bhagavad-gītā mentions five causes of defeat or victory. Of these five, daiva (providence) is the most powerful (na ca daivāt paraṁ balam). Bali Mahārāja knew the secret of how he had formerly been victorious because providence was in his favor. Now, since that same providence was not in his favor, there was no possibility of his victory. Thus he very intelligently forbade his associates to fight.