Shiva as Prajapati, vedhaah.
In the Taittiriya Aranyaka there is a mantra that Sayanacharya comments as being addressed to Parvathivallabha, Shiva:
There are countless scriptural sources where Rudra is addressed/referred to as Prajapati.
The Mahabharata has several such instances, out of which here are just a few:
॥ रुद्राभिषेकस्तोत्रम् महाभारतान्तर्गतम् ॥
कुमारगुरवे तुभ्यं नीलग्रीवाय वेधसे । पिनाकिने हविष्याय सत्याय विभवे सदा ॥ ५.८०.५७॥ ब्रह्मवक्त्राय सर्वाय शंकराय शिवाय च । नमोस्तु वाचस्पतये प्रजानां पतये नमः ॥ ५.८०.६२॥
The Shiva Sahasranama stotram of the Mahabharata too has this name:
Bhishma says, in the prelude to the SSS:
prakṛtiṃ puruṣaṃ caiva kṣōbhayitvā svatējasā|
brahmāṇamasṛjat tasmāddēvadēvaḥ prajāpatiḥ||6||
Within the stotram two occurrences:
abhivādyō mahākarmā tapasvī bhūtabhāvanaḥ|
unmattavēṣapracchannaḥ sarvalōkaprajāpatiḥ||4||
nakṣatravigrahamatirguṇabuddhirlayō’gamaḥ|
prajāpatirviśvabāhurvibhāgaḥ sarvagō’mukhaḥ||29||
The term ‘prajapati’ is generally understood to mean Brahma, the four-faced. The Amarakosha gives these names, among others, for Brahma:
स्रष्टा प्रजापतिर्वेधा विधाता विश्वसृट्विधिः। 34
The name ‘vedhaah’ is also important, for this name is also used for Shiva, even as the name ‘prajapati’ is. There are instances of ‘vedhaah’ being used for Shiva.
श्रीभगवानुवाच
नमस्ते शितिकण्ठाय नीलग्रीवाय वेधसे । (vedhase is the chaturthi vibhakti of vedhaah)
नमस्ते शोचिषे अस्तु नमस्ते उपवासिने ।। १३ ।।
That name appears in the Śivasahasranāma of the Śivapurāṇa:
http://sanskritdocuments.org/doc_trial/fortransfer/shivasahasranAmastotrashivapurANa_sa.html
वेधा विधाता धाता च स्रष्टा हर्ता चतुर्मुखः ।
कैलासशिखरावासी सर्वावासी सदागतिः ॥
The Shiva purana has been cited by Shankara in the Vishnu Sahasra Nama for the name ‘rudra’ as ‘shivah parama kaaranam.’ Sridhara Swamin has cited two verses from the Shvia Purana in the Vishnu purana bhashya, again to bring out Shiva’s paratva. Sri Raghavananda, a 13 CE commentator of the Bhagavatam and the author or several works, has cited several verses from the Shiva purana to bring out Shiva paratva in the ‘sarva mata sangraha’.
Sureshwaracharya has referred to Shankaracharya at the end of his Br.Up.Bhashya Vartika as ‘he who bears the name of vedhaah’:
तं वन्देऽत्रिकुलप्रसूतममलं वेधोऽभिधं मद्गुरुम् ॥
[In the mangala shloka for his Taittiriya Up. Bha.vartika too Sureshwara refers to Shankara as ‘bhava-naama-bhrti’, one who bears the name of ‘Bhava’, Shiva. Therefore it is undoubtedly clear that Sureshwara uses the word ‘vedhaah’ with reference to Shiva alone.]
Thus we see several instances of the name ‘Prajapati’ and ‘Vedhaah’, its synonym, used for Shiva. The above references also bring out the fact that Sayanacharya’s commentary on the Aranyaka mantra ‘prajapate…’ as a prayer to Shiva has the basis in Veda Vyasa and his purvacharyas.