Atheist

As for those who believe not in the signs of God, or that they shall ever attain His Presence, these of My mercy shall despair, and these doth a grievous chastisement await." And likewise He saith: "And they say, 'What! when we shall have lain hidden in the earth, shall we become a new creation?' Yea, they deny that they shall attain the Presence of their Lord." And likewise He saith: "They truly doubt the Presence of their Lord. He, verily, overshadoweth all things." And likewise He saith: "Verily, they who hope not to attain Our Presence, and find their satisfaction in this world's life, and rest on it, and who of Our signs are heedless -- these! their abode the fire, in recompense of their deeds!

Bahá’u’lláh, Epistle to the Son of the Wolf, p. 115

For they who turn away from their Lord in this day are in truth accounted amongst the dead, though to outward seeming they may walk upon the earth, amongst the deaf, though they may hear, and amongst the blind, though they may see, as hath been clearly stated by Him Who is the Lord of the Day of Reckoning: "Hearts have they with which they understand not, and eyes have they with which they see not...." They walk the edge of a treacherous bank and tread the brink of a fiery abyss. They partake not of the billows of this surging and treasure-laden Ocean, but disport themselves with their own idle words.

Bahá’u’lláh, Gems of Divine Mysteries, p. 48-49

Know thou for a certainty that whoso disbelieveth in God is neither trustworthy nor truthful. This, indeed, is the truth, the undoubted truth . . . Nothing whatever can deter such a man from evil, nothing can hinder him from betraying his neighbor, nothing can induce him to walk uprightly.

Bahá’u’lláh, Gleanings from the Writings of Bahá’u’lláh, p. 232-233

QUESTION: Is it permissible for a believer to marry an unbeliever?

ANSWER: Both taking and giving in marriage are permissible; thus did the Lord decree when He ascended the throne of bounteousness and grace.

Bahá’u’lláh, The Kitab-i-Aqdas, p. 131

The gates of Hell have opened wide to receive thee, O thou who hast turned away from thy Lord, the Unconstrained! Repair unto its fire, for it yearneth after thee.

Bahá’u’lláh, The Summons of the Lord of Hosts, p. 178

They that have disbelieved in God and rebelled against His sovereignty are the helpless victims of their corrupt inclinations and desires. These shall return to their abode in the fire of hell: wretched is the abode of the deniers!

Bahá’u’lláh, Gleanings from the Writings of Bahá’u’lláh, p. 284