Chapter 2 · The Yoga of Knowledge · Krishna said
Bhagavad Gita 2.32 — A door to heaven
यदृच्छया चोपपन्नं स्वर्गद्वारमपावृतम्। सुखिनः क्षत्रियाः पार्थ लभन्ते युद्धमीदृशम् ॥
yadṛcchayā copapannaṃ svargadvāramapāvṛtam | sukhinaḥ kṣatriyāḥ pārtha labhante yuddhamīdṛśam ||
Meaning
Fortunate are the warriors, Partha, who get such a war that comes on its own, like an open door to heaven.