Skandapurana 1.4.39.23

1.4.39.23

mahāṃti pātakānyāhurniraṃtaraphalāni ṣaṭ‌..
nābhinaṃdaṃti ye dṛṣṭvā śaṃkaraṃ na stuvaṃti ye.. 41.23 ..

They declare six great sins that bear unending fruit:
Those who, seeing Śaṅkara, do not rejoice, and those who do not praise him;