Sings Lord Krishna in Chapter Ten,Verse Twenty Three of Bhagavad Gita.

Sri Krishn is Shankar among Rudr. Shankar-“shanka-ar’’-may be understood as the condition in which there are no doubts and irresolutions.

Arjun,the disciple of Lord Krishn prays to Lord Krishn in Chapter Eleven,Verse forty three of Bhagavad Gita:

“tvamasya pūjyaśca gururgarīyān………the revered of all Gurus,”

which denotes that an accomplished revered Guru is in the purest form of Lord Shiva.

Ramcharit Manas also confirms in verse three of Baalkand:

वन्दे बोधमयं नित्यं गुरुं शङ्कररूपिणम्।
यमाश्रितो हि वक्रोऽपि चन्द्रः सर्वत्र वन्द्यते॥

I make obeisance to the eternal preceptor in the form of Lord Shankara,
who is all wisdom,
and resting on whose brow the crescent moon,
though crooked in shape,
is universally adored.

I too bow down in lotus feet of revered Gurudev at this most sacred occasion of Mahashivratri.

https://youtu.be/K48vPxeAh-c

Humble Wishes!
~mrityunjayanand~