Manusmriti

siva.sh/manusmriti/2/142

निषेकादीनि कर्माणि यः करोति यथाविधि । सम्भावयति चान्नेन स विप्रो गुरुरुच्यते ॥ १४२ ॥

sanskrit

That Brahmana, who performs in accordance with the rules (of the Veda) the rites, the Garbhadhana (conception-rite), and so forth, and gives food (to the child), is called the Guru (the venerable one).

english translation

niSekAdIni karmANi yaH karoti yathAvidhi | sambhAvayati cAnnena sa vipro gururucyate || 142 ||

hk transliteration by Sanscript