How it is possible to validate existing Pay to Public Key Hash transaction without public key?

How it is possible to validate existing Pay to Public Key Hash transaction without public key?

These are my understanding or assumptions.

Sign a document requires secret key and message only as below

SignDocument(secret key, message) => signature

And verification of signature requires public key, signature and message as below

VerifySignature(signature, message , public key)

Purpose of scriptPubKey is a script for validating signature for P2PKH transactions.

It is clear that we need public key in order to validate transaction but existing transaction data doesn't have public key data but hash of public key only.

I can easily understand Pay to Public Key transaction because public key is part of transaction data.

If public key is not stored in blockchain so how it is possible to validate P2PKH transaction without public key?

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