The material world is an illusory energy to deviate the living entities from the path of self-realization. Anyone who is in this material world is extremely anxious to get more and more things for sense gratification. Actually, however, the purpose of life is not sense gratification but self-realization.
His Divine Grace A. C. Bhaktivedanta Swami Prabhupada
Srimad-Bhagavatam 8.19.21, Purport

All seeking after joy is the function of the soul. When the desire for joy wakes up in our minds, we commit a blunder in running after worldly objects and enjoyment. It is only when we receive a spiritual sight of Krishna that we understand that His service must of necessity be the sole aim in life.
Srila Bhaktisiddhanta Sarasvati Thakura
Real and Apparent (Essay), p. 18

Man attempts to please the Lord for four reasons, according to his condition of life: from fear, for satisfying material aspirations, from a sense of duty, and from genuine attraction (raga). Those who take to worship of the Lord from fear, desire, or duty are not on such a pure level. Those who worship the Lord according to raga are real worshipers.
Srila Bhaktivinoda Thakura
Sri Chaitanya Sikshamrita, 1.10-11

Because a devotee of Lord Krishna is desireless, he is peaceful. Fruitive workers desire material enjoyment, jnanis desire liberation, and yogis desire material opulence; therefore they are all lusty and cannot be peaceful.
Sri Chaitanya Mahaprabhu
Sri Chaitanya-charitamrita, Madhya-lila 19.149

The Lord is the supremely compassionate reservoir of all transcendental qualities. Life after life may I serve Him with love, friendship, and sympathy, and may I cultivate such firm attachment for Him by the precious association of His devotees.
Sudama Vipra
Srimad-Bhagavatam 10.81.36

I offer my respectful obeisances unto Krishna, who has a transcendental form of bliss, eternity, and knowledge. I offer my respect to Him, because understanding Him means understanding the Vedas and He is therefore the supreme spiritual master.
Gopala Tapani Upanishad 1.1

The holy name of the Lord is supremely glorious.
Svetashvatara Upanishad 4.19

The Supreme has no material form made of flesh, marrow, and bones. He has His form not by virtue of practicing yoga but because He is the Absolute Lord. The personal from of the infallible, all-powerful Lord is real.
Varaha Purana (Cited in Brihad-bhagavatamrita 2.4.160, Commentary)