Srimad Bhagavatam

References to text SB 1.3.28
SB 1.3.28: All of the above-mentioned incarnations are either plenary portions or portions of the plenary portions of the Lord, but Lord Śrī Kṛṣṇa is the original Personality of Godhead. All of them appear on planets whenever there is a disturbance created by the atheists. The Lord incarnates to protect the theists.

Text №
“All these incarnations of Godhead are either plenary portions or parts of the plenary portions of the puruṣa-avatāras. But Kṛṣṇa is the Supreme Personality of Godhead Himself. In every age He protects the world through His different features when the world is disturbed by the enemies of Indra.”
Sri Caitanya Mahaprabhu Is the Supreme Personality of Godhead
CC 1.2.67
“All these incarnations of Godhead are either plenary portions or parts of the plenary portions of the puruṣa-avatāras. But Kṛṣṇa is the Supreme Personality of Godhead Himself. In every age He protects the world through His different features when the world is disturbed by the enemies of Indra.”
The Glories Of Lord Nityananda Balarama
CC 1.5.79
“ ‘All these incarnations of Godhead are either plenary portions or parts of the plenary portions of the puruᚣa-avatāras. But Kṛṣṇa is the Supreme Personality of Godhead Himself. In every age He protects the world through His different features when the world is disturbed by the enemies of Indra.’
Lord Sri Caitanya Mahaprabhu's Travels to the Holy Places
CC 2.9.143
“Of all Kṛṣṇa’s abodes, which do you think is the best?”
Lord Sri Caitanya Mahaprabhu Instructs Srila Rupa Gosvami
CC 2.19.102
“ ‘All these incarnations of Godhead are either plenary portions or parts of the plenary portions of the puruᚣa-avatāras. But Kṛṣṇa is the Supreme Personality of Godhead Himself. In every age He protects the world through His different features when the world is disturbed by the enemies of Indra.’
Lord Sri Caitanya Mahaprabhu Instructs Sanatana Gosvami in the Science of the Absolute Truth
CC 2.20.156
“ ‘All these incarnations of Godhead are either plenary portions or parts of the plenary portions of the puruᚣa-avatāras. But Kṛṣṇa is the Supreme Personality of Godhead Himself. In every age He protects the world through His different features when the world is disturbed by the enemies of Indra.’
How All the Residents of Varanasi Became Vaishnavas
CC 2.25.134