Manusmriti

siva.sh/manusmriti/2/36

गर्भाष्टमेऽब्दे कुर्वीत ब्राह्मणस्यौपनायनम् । गर्भादेकादशे राज्ञो गर्भात् तु द्वादशे विशः ॥ ३६ ॥

sanskrit

In the eighth year after conception, one should perform the initiation (upanayana) of a Brahmana, in the eleventh after conception (that) of a Kshatriya, but in the twelfth that of a Vaisya.

english translation

garbhASTame'bde kurvIta brAhmaNasyaupanAyanam | garbhAdekAdaze rAjJo garbhAt tu dvAdaze vizaH || 36 ||

hk transliteration by Sanscript