Śaṅkarācārya is the incarnation of Lord Śiva, and he's a great devotee. Śaṅkara... Vaiṣṇavānāṁ yathā śambhuḥ: "There are many devotees of the Lord, but the foremost devotee is Lord Śiva." And he has got a disciplic succession which is called Viṣṇu Svāmī-sampradāya. So Śaṅkarācārya was covered devotee. He's covered devotee. His aim was to bring men to the standard of devotional service, but the time and circumstances in which he was preaching, he could not place his real object because they were unable to understand. At last, at the end of his life, he composed so many poetries in praise of Vṛndāvana-līlā, and especially his very famous Catpar pandika (?), that is, he has stated,
- bhaja govindaṁ bhaja govindaṁ
- bhaja govindaṁ mūḍha-mate
- prāpte sannihite kāla maraṇe
- na hi na hi rakṣati ḍukṛñ-karaṇe
"My dear foolish brothers, you kindly worship Kṛṣṇa, Govinda..." Thrice he has said, bhaja govindaṁ bhaja govindaṁ bhaja govindaṁ mūḍha-mate. Mūḍha-mate means "You foolish nonsense, you kindly worship Govinda." Why? Now, prāpte sannihite kāla maraṇe: "When death will be nearer, your this grammatical interpretation, ḍukṛñ karaṇe, this pratha (?), that pratha (?), arguing, jugglery of words, will not save you, will not save you. You please worship Govinda." That is his instruction. And there are many others.
So Śaṅkarācārya was a covered devotee. He was devotee. Somebody accuses Śaṅkarācārya that he was covered Buddhist. But so far I am concerned, I say that Śaṅkarācārya was covered devotee.