If, after the making of any will, the testator shall execute a later will which expressly or by necessary implication revokes the earlier will, the revocation of the later will shall not revive the earlier will, unless the revocation is in writing and declares the intention of the testator to revive the earlier will, or unless, after such revocation, the earlier will shall be reexecuted. Oral republication of itself shall be ineffective to revive a will.