Incarnation of Qualified (Saguna) Brahma The two aspects of God

य दा यदा हि धर्मस्य ग्लानिर्भवति भारत ।  अभ्युत्थानमधर्मस्य तदात्मानं सृजाम्यहम् ॥ (गीता ४.७) Whenever, there is a decline in righteousness and an upsurge in unrighteousness, O Arjuna, I then manifest Myself.

परित्राणाय साधूनां विनाशाय च दुष्कृताम् । धर्मसंस्थापनार्थाय सम्भवामि युगे युगे ॥ (गीता ४.८) For the protection of the good, for the destruction of the wicked and for the establishment of righteousness, I manifest myself from age to age.

जब जब होइ धरम कै हानी । बाढहिं असुर अधम अभिमानि । (रामचरितमानस १:१२०:३) तब तब प्रभु धरि बिबिध सरीरा । हरहिं कृपानिधि सज्जन पीरा ॥ (रामचरितमानस, १:१२०:४)

असुर मारि थापहिं सुरन्ह राखहिं निज श्रुति सेतु । ( रामचरितमानस १:१२१)

 Whenever virtue declines and vile and arrogant demons multiply; the gracious Lord assumes various (transcendent) forms and relieves the distress of the virtuous. Killing the demons, He reinstates the gods, and preserves the bound of propriety fixed by the Vedas.

न जायते म्रियते वा कदाचिन्नायं

भूत्वा भविता वा न भूयः ।

अजो नित्यः शाश्वतोऽयं वपुराणो

न हन्यते हन्यमाने शरिरे ॥ (गीता २.२० )

 For the soul there is neither birth nor death, nor does it come into existence after having been born. It is unborn, eternal, constant and primeval. It is not killed even when the body is slain.