Devibhagavatapurana 11.15.97

11.15.97

acchidrānapi sacchidrān kuryuḥ kevalavaiṣṇavāḥ |
acchidrakaraṇe teṣāṃ pratyavāyo na vidyate ||

Those who are Vaisnavas in name only can use Ûrdhapundra of both the kinds, with or without any empty space. They incur no sin if they use one without an empty space. But those who are My good devotees, incur sin if they do not keep an empty space between the two vertical lines (in the Ûrdhapundra three vertical lines are used). The Vaisnavas who use excellent vertical rod like Ûrdhapundras keeping an empty space in the middle and uttering the mantra “Kesvâya Namah” build My Temple there. In the beautiful middle space of Ûrdhapundra, the Undecaying Visnu is playing with Laksmî. That wretch, the twice-born who uses Ûrdhapundra without any empty apace kills Visnu and Laksmî, seated there. The stupid who uses Ûrdhapundra without a vacant space goes successively to twenty-one hells. The Ûrdhapundra should be of the size of a clear straight rod, lotus, flame, a fish with sharp straight edges and with vacant spaces between them. O Great Muni! The Brâhmana should always use the Tripundra like the lock of hair on the crown of his head and like his Sacrificial thread; otherwise all his actions will be fruitless. Therefore in all ceremonies and actions the Brâhmanas ought to use Ûrdhapundras of the form of a trident, a circle or of a square form. The Brâhmana who knows the Vedas is never to use the semi-moonlike mark (Tilak) on his bead. The man who is of the Brâhmin caste and follows the path of the Vedas should not even by mistake use any other mark than those above-mentioned. Other sorts of pundras (marks) that are mentioned in other Vaisnava S’âstras for the attainment of fame, beauty, etc., the Veda-knowing Brâhmanas should not use them. The Vaidik Brâhmanas should not use even in error any other Tilaks than the curved Tripundras
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If, out of delusion, the man, following the path of the Vedas, uses other sorts of Tripundras, he would certainly go down to hell.