Srimad-Bhagavatam: Canto 8 - Chapter 1 - Verse 20
Sanskrit:
नैतत् परस्मा आख्येयं पृष्टयापि कथञ्चन ।सर्वं सम्पद्यते देवि देवगुह्यं सुसंवृतम् ॥ २० ॥
ITRANS:
naitat parasmā ākhyeyaṁpṛṣṭayāpi kathañcanasarvaṁ sampadyate devideva-guhyaṁ susaṁvṛtam
Translation:
O lady, even if someone inquires, you should not disclose this fact to anyone. That which is very confidential is successful if kept secret.