Bhagavad Gita: Chapter 2, Verse 32

यदृच्छया चोपपन्नं स्वर्गद्वारमपावृतम् ।
सुखिनः क्षत्रियाः पार्थ लभन्ते युद्धमीदृशम् ॥ २-३२ ॥

yadṛcchayā copapannaṁ svarga-dvāram apāvṛtam
sukhinaḥ kṣatriyāḥ pārtha labhante yuddham īdṛśam 2.32

O Partha, happy are the kshatriyas to whom such fighting opportunities to defend righteousness come unsought, opening for them the doors of the heavenly planets.