Witnesses are not required to enter into a valid agreement of sale for land. Section 2 of the Alienation of Land Act merely requires that a valid deed of alienation must be contained in writing and signed by the parties thereto or their agents.
The only purpose of a witness is to confirm and verify the signature and identity of the party which signature he witnesses. Such witness does not in any way confirm, verify or support the content of the document in any way.
The practice to require witnesses to initial each page and/or where amendments have been made along with parties does not affect the validity of the agreement in any way and is also not a statutory requirement. The aim therein is purely to remove ambiguity as to whether the parties concerned have indeed signed the relevant page and/or amendment.