Point One: You yourself realize what is wrong.
Point Two: The clause mentioned has no value; it is not on stamp paper and not signed by two parties at the same point with elaboration of the details. It is arbitrary, and since such things are not discussed during hiring, it has no legal value (those are mere bindings on the one standing at the receiving end). One does not leave a job and join another just to get nailed.
Point Three: A verbal warning is just an abuse nowadays, especially in corporates bound by social responsibilities. They can't hire and fire at will. I should not write, but I am simply frustrated by such actions. How can they harass a person at their whim who can be a breadwinner for more than one? Approach your HR Department (but make sure you stand on substantial grounds). Treating people like cattle is not permissible at any cost.
Hemant, why don't you put this in writing, like:
Dear ...,
Regarding the verbal warning on ... issue, I will make sure to uplift my work standards as per your requirements & wishes.
Thanks,
Hemant (next time it happens, make sure to CC your management)
Point Four: Ethically, they should mention what you are lacking...
Give time to redo things...
If they do not... (leave such a company that does not listen, react, and act before they fire you).
I personally feel probation is a useless burden on newcomers; before today, I never saw any company taking action (apart from severe financial, sexual harassment).
My point is if I ask for training costing much, then it is okay for the company to ask for a bond, and if I fail, then ask for damages. But in this case, one gets an offer letter, leaves the present job, joins another, and on the joining date, he is asked to sign something so useless, and that too at a time when he is not in a position to negotiate.
Hemant, I do not want you to have a fight (literally). See, if you are not fit for this job, I assure you are not fit for any job (hope you are getting me). The labor court will kill your chances to work in the organization and elsewhere (Whistleblower is a myth).
My remarks are based on the facts mentioned by Hemant in his query, and I might be wrong if he is hiding something.
Hemant, are you sure you do not indulge in any underwater activities?