Bhagavad Gita · Bhakti YogaChapter 12, Shloka 3 (12.3)

Shankaracharya — the definition of upasana (worship). upāsanaṃ nāma yathāśāstram upāsyasya arthasya viṣayīkaraṇena sāmīpyam upagamya tailadhārāvat samānapratyayapravāheṇa dīrghakālaṃ yat āsanam — to approach the object of worship as the scriptures teach, and to remain for a long time in an unbroken flow of the same thought, like a stream of oil; kūṭasthaṃ — kūṭa = maya (virtue outside, flaw within), and this one abides as its overseer; or rāśir iva sthitaṃ — steady like a heap.

Acharya Ramanuja. akṣaraṃ pratyagātmasvarūpaṃ anirdeśyaṃ dehād anyatayā devādiśabdānirdeśyam — because it is distinct from the body, it cannot be designated by words like "god" or "human"; kūṭasthaṃ sarvasādhāraṇaṃ — the same in all bodies; acalaṃ … dhruvaṃ nityam.