Bhagavad Gita 13.10
असक्तिरनभिष्वङ्गः पुत्रदारगृहादिषु। नित्यं च समचित्तत्वमिष्टानिष्टोपपत्तिषु।।13.10।।
asaktiranabhiṣvaṅgaḥ putradāragṛhādiṣu| nityaṃ ca samacittatvamiṣṭāniṣṭopapattiṣu||13.10||
asaktiranabhishvangah putradaragrihadishu nityam ca samacittatvamishtanishtopapattishu13.10
Meaning
...non-attachment, absence of clinging to son, wife, home, and the rest, constant even-mindedness in desirable and undesirable events...
असक्ति तथा पुत्र, पत्नी, गृह आदि में अनभिष्वङ्ग (तादात्म्य का अभाव); और इष्ट और अनिष्ट की प्राप्ति में समचित्तता।
This is verse 10 of 35 in Chapter 13 (Kshetra Kshetrajna Vibhaga Yoga) of the Bhagavad Gita.