BṚHADĀRAṆYAKA UPANISHAD · 6.4.10

अथ याम् इच्छेन् न गर्भं दधीतेति तस्याम् अर्थं निष्ठाय मुखेन मुखं संधायाभिप्राण्यापान्यात् ।
इन्द्रियेण ते रेतसा रेत आदद इति ।
अरेता एव भवति ॥

atha yām icchen na garbhaṃ dadhīteti tasyām arthaṃ niṣṭhāya mukhena mukhaṃ saṃdhāyābhiprāṇyāpānyāt ।
indriyeṇa te retasā reta ādada iti ।
aretā eva bhavati ॥

Now, the woman whom one may desire with the thought, 'May she not conceive offspring!'--after coming together with her and joining mouth with mouth, he should first inhale, then exhale, and say: 'With power, with semen, I reclaim the semen from you!' Thus she comes to be without seed.

Robert Ernest Hume · The Thirteen Principal Upanishads (1921), Bṛhadāraṇyaka VI.4