Shivastotravalli 1.11:

भवद्भक्त्यमृतास्वादाद्धोधस्य स्यात्परापि या। दशा सा मां प्रति स्वामिन्नासवस्ये शुक्तता।।

"O ruler of this world! Without your devotion, any higher stage of knowledge is meaningless just like rotten wine."

Shivastotravalli 1.12:

भवद्भक्तिमहाविद्या येषामभ्यासमागता। विद्याविद्योभयस्यापि त एते तत्त्ववेदिनः।।

"O Shankara! Who continuously practice the great knowledge which is nothing but your devotion, Only those great people will have the depth knowledge of spiritual knowledge and half-cooked knowledge."

Commentaries:

Akshay Ji: Devotion to Lord Shiva is ultimate. Devotion means Lord Shivas words is your life and thats called devotion. Such devotion is literally the highest knowledge.

MindDissolved Ji: Without wisdom and devotion to My Lord My God Shiva. Knowledge is just a information. People have bookish knowledge and pretend to be knowledgeable. This people are hallow internally. True knowledge is surrendered devotion with love towards my Lord My God Shiva.