Srimad-Bhagavatam: Canto 7 - Chapter 1 - Verse 21

Sanskrit:

आरोप्याङ्कमवघ्राय मूर्धन्यश्रुकलाम्बुभि: ।आसिञ्चन् विकसद्वक्त्रमिदमाह युधिष्ठिर ॥ २१ ॥

ITRANS:

āropyāṅkam avaghrāyamūrdhany aśru-kalāmbubhiḥāsiñcan vikasad-vaktramidam āha yudhiṣṭhira

Translation:

Nārada Muni continued: My dear King Yudhiṣṭhira, Hiraṇyakaśipu seated Prahlāda Mahārāja on his lap and began smelling his head. With affectionate tears gliding down from his eyes and moistening the child’s smiling face, he spoke to his son as follows.

Purport:

If a child or disciple falls at the feet of the father or spiritual master, the superior responds by smelling the head of the subordinate.