Devibhagavatapurana 7.36.27

7.36.27

tasmātsarvaprayatnena śrīguruṃ toṣayennaga |
kāyena manasā vācā sarvadā tatparo bhavet ||

So the Guru must be served with all the cares that are possible by body, mind, and word one should always please Him. Otherwise he becomes ungrateful and he is not saved.