The verse from Bhagavata 10.88.5 reads as :
harir hi nirguṇaḥ sākṣāt puruṣaḥ prakṛteḥ paraḥ
sa sarva-dṛg upadraṣṭā taṁ bhajan nirguṇo bhavet
What does the word nirguna stand here and what is the justification?
The verse from Bhagavata 10.88.5 reads as :
harir hi nirguṇaḥ sākṣāt puruṣaḥ prakṛteḥ paraḥ
sa sarva-dṛg upadraṣṭā taṁ bhajan nirguṇo bhavet
What does the word nirguna stand here and what is the justification?
First, the context of the verses makes it clear that it is talking about modes of material natures(3 gunas)
See for eg:
SB 10.88.3: Śrī Śukadeva said: Lord Śiva is always united with his personal energy, the material nature. Manifesting himself in three features in response to the entreaties of nature’s three modes, he thus embodies the threefold principle of material ego in goodness, passion and ignorance.
SB 10.88.4: The sixteen elements have evolved as transformations of that ego. When a devotee of Lord Śiva worships his manifestation in any one of these elements, the devotee obtains all sorts of corresponding enjoyable opulences.
Now, occurs the verse
harir hi nirguṇaḥ sākṣāt puruṣaḥ prakṛteḥ paraḥ sa sarva-dṛg upadraṣṭā taṁ bhajan nirguṇo bhavet
Since, it is already described in Bhagavatam that Hari has many qualities.
For eg:
ete cānye ca bhagavan nityā yatra mahā-guṇāḥ prārthyā mahattvam icchadbhir na viyanti sma karhicit
SB 1.16.29: The Lord possesses many other transcendental qualities which are eternally present and never separated from Him.
Considering the context in which 10.88.5 occurs and the previous descriptions of transcendental qualities of Lord, nirguna can mean above material gunas.
Therefore 10.88.5 can be aptly translated as:
Lord Hari however, the primeval purusa, is transcendental to material nature and absolutely untouched by the modes. He is the [inner] witness seeing everything. By worshiping Him one is freed from [the influence of] the gunas.
Chaitanya Mahprabhu says this in 20th Chapter of madhya lila, Chaitanya Charitamrta
‘śiva’ — māyā-śakti-saṅgī, tamo-guṇāveśa māyātīta, guṇātīta ‘viṣṇu’ — parameśa
and then quotes the 10.88.5.
Nirguna is interpreted in the same manner by Jiva Goswami, Sanatan Goswami, Viraraghavacharya in the commentary to this verse.
I highly doubt if any advaitin commentator on BHAGAVATAM would have interpreted nirguna to mean 'devoid of qualities' in this straight forward verse.
So, thinking dispassionately,fitting the definition that nirguna means 'quality-less' or 'devoid of qualities' makes no sense and is self contradictory in this context, nirguna translated as 'untouched by three material modes/material qualities' seems apt.
This verse from Srimad-Bhagavatam has to be understood remembering the context, the commentaries of Sridhara Swami, and what Sri Krishna Himself says about His 'Nirguna Swarupa'.
Context
King Parikshit asked Sukdeva: Lord Shiva is a yogi devoid of any luxuaries and Lord Hari is the Husband of Lakshmi, the Goddess of Wealth.Then why do the devotees of Lord Shiva become wealthier while the devotees of Lord Hari get poorer? (10.88.1)
In reply, Sri Sukadeva said: Lord Shiva is ever associated with His Shakti Uma. By three gunas, He is expressed by three types of egos : Sattvika, Rajasika and Tamasika. When a devotee worships Shiva as embodiment of any of the three gunas, he receives the fruits accordingly and becomes wealthier and luxurious.
While Lord Hari is devoid of these three material gunas and is beyond all gunas.He is Purna, Purushottama, Omniscient and Ever-Witness. Those who worship Him becomes free from all the gunas and goes beyond the gunas.
Sridhara Swami's commentary
Sridhara Swami mentions in this context that the worshippers of Shiva and Brahma get bhoga and slowly proceeds to Mukti (shanair moksha).While the worshippers of Vishnu gets Mukti quickly.
Then Sridhara Swami points out that the quarrel between the devotees of Brahma, Vishnu and Shiva in this regard is just delusion (tadbhaktAnam tu kalaho mohamatram iti).
How Sri krishna explains 'Nirguna'
Now what does 'Nirguna' mean? Sri Krishna says to Yudhisthira:
The person on whom I shower my grace (will become poorer) as I shall remove all his wealth slowly. He tries first to regain the lost wealth, but fails by my grace.He then becomes totally dispassionate and gradually mixes with my devotees and remains in their company and serves them. Therefore I become more graceful to him and liberate him from the world.(10.88.8-9).
What happens to the devotee then? Sri Krishna says:
tad (that) brahma(Brahman) paramam (Absolute) sukshmam (Subtle) chinmatram (as only Pure Consciousness) sad (Eternal)anantakam (Endless).Vijnaya (By knowing)AtmatayA (by the Self) dhirah (Wise Ones) sansArad (from the worldliness) parimuchchyate (is liberated). Meaning: By knowing Absolute Brahman that is Very Subtle,Eternal, Endless, and Just Pure Consciousness by his Self, the wise ones are liberated from worldliness.(10.88.10)
Here Sri Krishna Himself explains what is meant by the word 'Nirguna'. Nirguna means the very Subtle form which is Existence, and Pure Consciousness.
We see that there is no fundamental difference between Sri Krishna's description of 'Nirguna' and Adi Sankara's concept of 'Nirguna'.
Sri Krishna then says that many devotees find it difficult to attain Him like this and start worshipping the deities for material gain.
Adi Sankara would not object to this at all!
Sri Jiva Goswami in His Sri Vaishnava Toshini Commentary and Sri Radhavinoda Goswami in his Bhagavatamrita Subcommentary do not use a siingle word that denigrates Shiva or any other deity. Moreover, its mentioned that Lord Shiva has a 'Tatpurusha' Form Who grants Self-Knowledge.
Lord Shiva has one such form while all the Forms of Lord Hari are beyond worldly qualities and are beyond all qualities."All of them correspond to the KEVALA and NIRGNA svarupas mentioned in the Upanishads".
(Reference : Srimad-Bhagavatam, Canto 10, Chapter 12, Commentary by Sridhara Swami and Sri Jiva Goswami and subcommentary by Radhavinoda Goswami, Mahesh Library Kolkata, 1st Ed.,pages 255-263.)