Bhagavad Gita 2.32

यदृच्छया चोपपन्नं स्वर्गद्वारमपावृतम्।सुखिनः क्षत्रियाः पार्थ लभन्ते युद्धमीदृशम् ॥२.३२॥

yadṛcchayā copapannaṃ svargadvāramapāvṛtamsukhinaḥ kṣatriyāḥ pārtha labhante yuddhamīdṛśam

Happy are the Kshatriyas, O Arjuna! who are called to fight in such a battle that comes of its own accord as an open door to heaven.

गीता