Tell me the reason please.
Learning about your faith from people with the requisite reading is always a pleasure.
Cheers, Doc
Janmana jayate shudrah
Samskarad dvija ucyate
Vedapathi bhaved viprah
Brahma janati brahmanah
Meaning,
One is a Shudra by birth
By observing Sanskara one becomes a Dvija
By studying the Vedas one becomes a Vipra
One who knows Brahman is a Brahmana
In short, anyone who takes Deeksha is twice born. Deeksha itself can be in may forms. From upanayana to simply chanting a mantra specific number of times.
Sanskara / Samskara means consciously joining your action with the divine. One becomes a Hindu by doing so.
There are 48 Samskara mentioned in the scriptures.
Garbha daana, Pumsavana, Seemontonnayana, Jaata Karma,Naama karana, Anna praashana, Choula, Upanayana, Four Veda Vrataas, Snaataka, Saha dharma charini samyoga; Pancha yajnaanushthaana viz. of Deva-Pitru-Manushya-Bhuta- Braahma; Ashtakaa paarvana, Shraaddha, Shravani, Agrahaayani, Chaitri and Ashviyuji being Seven Paaka Yajnas; Seven Haviryajnas viz. Agnyaadheya, Agni hotra, Darsha purna momths, Agraayana, Chaturmaasya, nirudha, pashubandha and Soatramani; and Seven Somas viz. Agnishtoma, Atyagnishtoma, Ukthya, Shodashi,Vaajapeya, Atiraatra and Aapteya.
These are basic Karma (actions) that a person performs and consciously linking them to devine makes one a Hindu. The "how to do that" is where Deeksha comes in or where study of the scripture or a Guru/ Acharya comes in.