N.J. Stat. Ann. § 40:54-19.5

All interest, income or profit which may be realized by the board of trustees from the investment, pursuant to this or any other act, of any such funds shall be added to the principal of such funds and be used for the same purpose or purposes for or toward which the principal gift or bequest was made until the purpose or purposes for or toward which such gift or bequest was made shall have been accomplished.