You can find full text of the proposal on thomas.loc.gov
S.AMDT.106 to H.R.1 To amend the Internal Revenue Code of 1986 to provide a Federal income tax credit for certain home purchases.
Sponsor: Sen Isakson, Johnny [GA] (introduced 2/3/2009)
It applies to a purchase “of a qualified principal residence”. Furthermore:
In the event that a taxpayer–
“(A) disposes of the principal residence with respect to which a credit was allowed under subsection (a), or
“(B) fails to occupy such residence as the taxpayer’s principal residence,
at any time within 24 months after the date on which the taxpayer purchased such residence, then the tax imposed by this chapter for the taxable year during which such disposition occurred or in which the taxpayer failed to occupy the residence as a principal residence shall be increased by the amount of such credit.