Devibhagavatapurana 1.4.9

1.4.9

tiraścāmapi yatprema putre samabhilakṣyate |
kiṃ citraṃ yanmanuṣyāṇāṃ sevāphalamabhīpsatām ||

Oh! What wonder is there, when the birds have so much filial affection towards their child, that men, who want services from their sons, would show their affection towards their sons! This pair of sparrows will not perform the happy marriage of their young one and will not see the face of their son’s wife; nor when they will grow old, that their child would become very religious and serve them to attain great merits in Heaven. Nor do they expect that their child would earn money and satisfy them nor the child would perform when they die, their funeral obsequies duly and help them in their sojourn in the next world; nothing of all these. Nor will the child perform the S’râdh ceremony at Gayâ; nor will the child offer the oblation of a blue bull on the day of offering the sacrifice to its ancestor (the bull is then let loose and held sacred); yet the pair of sparrows have so much affection towards their young one! Oh! in this world to touch the body of the son, especially to nurture the sons, is the highest happiness in life.