Let us remind ourselves of the relevant section of a verse in
the Bhadrāvudhamāṇavappucchā of the Pārāyanavagga of the
Sutta Nipāta:
Yaṃ yaṃ hi lokasmiṃ upādiyanti,
ten' eva Māro anveti jantuṃ.
"Whatever thing they grasp in this world,
By that itself Māra pursues a man."
Because of grasping, there is becoming or existence and
with it birth, decay and death, etc., follow suit, all due to crav-
ing. That is the deep idea behind the Buddha's definition of the
five grasping groups in terms of Māra.
In fact, these six sense-spheres, the six bases, are within the
juris-diction of Māra. This is evident from Māra's own words
in the Kas-sakasutta of the Sagāthakavagga of the Saṃyutta
Nikāya. [SN 4.19
http://www.accesstoinsight.org/tipitaka/sn/sn04/sn04.019.than.html]
Once, when the Buddha was admonishing the monks with
a sermon on Nibbāna, it occurred to Māra, the Evil One: "Now
this recluse Gotama is admonishing the monks and the monks
are listening attentively. I must go and blind their eye of wis-
dom." With this evil intention, he came there in the guise of a
farmer, carrying a plough on his shoulder, a goad in his hand,
with dishevelled hair and muddy feet, and asked the Buddha:
"Recluse, did you see my oxen?" Then the Buddha retorted:
"What is the use of oxen for you, Evil One?" Māra understood
that the Buddha had recognized him and came out with the fol-
lowing boast of his superiority:
Mam eva, samaṇa, cakkhu, mama rūpā,
mama cakkhusamphas-saviññānāyatanaṃ, kuhiṃ me, samaṇa,
gantvā mokkhasi?
Mam eva, samaṇa, sotaṃ ... Mam eva, samaṇa, ghānaṃ
...Mam eva, samaṇa, jivhā ... Mam eva, samaṇa, kāyo ...
Mam eva, samaṇa, mano, mama dhammā, mama
manosamphas-saviññānāyatanaṃ, kuhiṃ me, samaṇa, gantvā
mokkhasi?
"Mine, O recluse, is the eye, mine are the forms and mine
the sphere of eye-contact, where will you, recluse, go to escape
me?
Mine, O recluse, is the ear ... Mine, O recluse is the nose ...
Mine, O recluse is the tongue ... Mine, O recluse is the body ...
Mine, O recluse is the mind, mine are the mind-objects and
mine the sphere of mind-contact, where will you, recluse, go to
escape me?"
Now this is how the Buddha responded to that challenge:
Taveva, pāpima, cakkhu, tava rūpā, tava
cakkhusamphassaviñ-ñāṇāyatanaṃ, yattha ca kho, pāpima, n'atthi cakkhu, n' atthi rūpā, n' atthi cakkhusamphassaviññāṇāy-
atanaṃ, agati tava tattha pāpima.
Taveva, pāpima, sotaṃ ... Taveva, pāpima, ghāṇaṃ ...
Taveva, pāpima, jivhaṃ ... Taveva, pāpima, kāyaṃ ...
Taveva, pāpima, mano,
tava dhammā, tava manosamphassaviñ-ñāṇāyatanaṃ, yattha ca
kho, pāpima, n' atthi mano, n' atthi dhammā, n' atthi manosam-
phassaviññāṇāyatanaṃ, agati tava tattha pāpima.
"Yours, O Evil One, is the eye, yours are the forms and
yours the sphere of eye-contact, but where there is no eye, no
forms and no sphere of eye-contact, there you cannot go, Evil
One.
Yours, Evil One, is the ear ... Yours, Evil One, is the nose ...
Yours, Evil One, is the tongue ... Yours, Evil One, is the body
...
Yours, Evil One, is the mind, yours are the mind-objects and
yours the sphere of mind-contact, but where there is no mind, no
mind-objects and no sphere of mind-contact, there you cannot
go, Evil One."
From the Buddha's reprisal to Māra's challenge, we can well
infer that there indeed is a place to which Māra has no access.
That is none other than the cessation of the six sense-spheres.
Since it is something realizable, it is referred to as a `sphere'
in such contexts as, for instance, in the discourse on Nibbāna
beginning with the words atthi, bhikkhave, tad āyatanaṃ,
[Ud 8.1
http://www.accesstoinsight.org/tipitaka/kn/ud/ud.8.01.irel.html]
"there is, monks, that sphere", etc.