In this page, 321, first verse 20, states the birth of Hariharaputra, shAstra: After the images, below, the English gist is given.


Birth of MahāŚāstā
Translation:
Indra says, "In the past, when both the Devas and Asuras churned the ocean, and the nectar (Amṛta) emerged from it, Lord Viṣṇu took the form of Mohinī, enchanted the Asuras, quickly distributed the nectar to the Devas, and made them consume it."
At that moment, to see Mohinī, Maheśvara appeared there. She was extraordinarily beautiful, with enchanting, restless eyes, radiant like an unwavering streak of lightning. Her beauty was mesmerizing, like a flashing yet steady bolt of lightning. She had a slender waist adorned with captivating, pearl-studded ornaments and a chest that enhanced her charm.
Seeing Mohinī, Parameśvara desired to unite with her. Overcome with desire, he said, "O beautiful one with an exquisite form! I wish to unite with you."
Hearing this, Mohinī, who understood his intent, responded to Parameśvara.
Mohinī shyly lowered her gaze and said, "O Parameśvara! How can you unite with me? I am, in fact, Nārāyaṇa. I have now assumed the form of Mohinī."
Hearing this, Parameśvara responded, "Are you not the masculine energy (Puruṣa Śakti) among my four divine powers?"
Parameśvara continued, "That is why, in the past, I united with you and brought forth Brahmā Deva. In the Dāruka forest, you also assumed the form of Mohinī in a similar manner."
"O beloved! At that time, was it not you who desired to attain me? O beautiful one! Did I not say that I would unite with you and rejoice?"
"Therefore, you are indeed worthy of joining me again and again."
Even after hearing these words, Mohinī, who was unwilling for union, hesitated. At that moment, Under the teak tree in Jambūdvīpa, the extraordinarily beautiful Mohinī was forcefully pulled close, and Parameśvara swiftly united with her in passionate lovemaking. (12)
Unable to withstand the intense force of his vigorous union, Mohinī began sweating profusely and, overcome by the strain, started vomiting from time to time. (13)
"O Indraṇī! That vomited liquid transformed into a river called Gandaki, and in its waters, worms known as Vajradanta were born." (14)
Those worms build their nests silently using the soft clay found in the river, binding it together with their saliva. (15)
Whenever the river experiences a strong current and the water flows rapidly, these worms perish. Their nests float on the water’s surface and drift away. (16)
At that time, some people from that region cast nets into the river to catch these floating nests. They extract the gold that is found in the center of the nests and sell them. (17)
"O beloved! Those very worm-built nests are now known as Shālagrāma stones. Since they were formed from Viṣṇu's vomited fluid, they became famous as sacred images associated with Viṣṇu." (18)
"Therefore, even today, in this world, the revered Shālagrāma stones from the Gandaki River are used by great sages in the worship of Parameśvara's Yoni Pītha, known as Avudaiyar." (19)
"Due to this divine connection, the son born from both Śiva and Viṣṇu came to be known as Śāstā or Hariharaputra (the son of Hari and Hara).” (20)
Ajamukhi, seeing him, asked angrily, "Who are you?" (52)
Mahakala replied, "I am a servant of that great Śāstā, the ruler of this world, who was born to Viṣṇu—the supreme Śakti known as Puruṣa Śakti—and who serves Parameśvara, the one who rides the white elephant and wears the moon upon his head. What can you possibly do to me? Release this woman, who is worthy of worship!"
Hearing these words, the wicked Ajamukhi, filled with rage, grabbed her trident (Shula) and hurled it at him with great force. (53-54)
~Skanda Purāṇam Śaṅkara Saṃhitā Sambhava khanda -Asura Kāṇḍa Ch-13