The Mukhya Upaniṣads

Kauṣītaki · Adhyāya 2 · Kauṣītaki 2.1

Passage 10

अथ संवेशञ्जायायै हृदयमभिमृशेद्यत्ते सुसीमे हृदये हितमन्तः प्रजापतौ मन्येऽहं मां तद्विद्वांसं तेन माहं पौत्रमघं रुदमिति न हास्मत्पूर्वाः प्रजाः प्रैतीति ॥ १० ॥

In plain words

Then, when he is about to lie down, let him touch his wife's heart with the words: "That which is set within thy heart, O well-parted one, within Prajāpati — I think that I know it; by it may I never weep for the affliction of a child." Before him his children do not depart.