One verse

Srimad Bhagavatam 7.15.28

7.15.28

षड्‌‌वर्गसंयमैकान्ता: सर्वा नियमचोदना: । तदन्ता यदि नो योगानावहेयु: श्रमावहा: ॥ २८ ॥

sad-varga-samyamaikantah sarva niyama-codanah tad-anta yadi no yogan avaheyuh sramavahah

sat-varga
the six elements, namely the five working senses and the mind
samyama-ekantah
the ultimate aim of subjugating
sarvah
all such activities
niyama-codanah
the regulative principles further meant for controlling the senses and mind
tat-antah
the ultimate goal of such activities
yadi
if
no
not
yogan
the positive link with the Supreme
avaheyuh
did lead to
srama-avahah
a waste of time and labor

Ritualistic ceremonies, regulative principles, austerities and the practice of yoga are all meant to control the senses and mind, but even after one is able to control the senses and mind, if he does not come to the point of meditation upon the Supreme Lord, all such activities are simply labor in frustration.