There are many halachic chazakas. Most of them are halachic assumptions, such as:
- Keeping things the way they always were - Either financial (Chezkas Marei Kama) or religious (Chezkas Tahara, Chezkas Tuma - that we assume that once something was in one state, it stays that way until we bring proof otherwise).
- Interpersonal assumptions - e.g Chazaka She'ein Adam Meiz Panav (we assume a borrower won't lie completely to his lender), Milsa D'avida Le'Gluiya (people don't lie when their lie will be caught), etc.
What is the source of these Chazakas. Is it a Halacha LeMoshe MiSinai or is it a Sevara? If it is a Sevara, are any proofs brought that these Sevaras are true?