Ruling on the riddle: “Who are those who speak the truth but their destination is Hell?”
Question

                Who are those who speak the truth but their destination is Hell?.
Praise be to Allah.
      It should be noted that truthfulness is a means of 
      salvation in this world and in the Hereafter, and lying is a cause of 
      doom. 

    Muslim (2607) narrated that Ibn Mas‘ood (may Allah be pleased 
    with him) said: The Messenger of Allah (blessings and peace of Allah be upon 
    him) said: “I enjoin you to be truthful, for truthfulness leads to 
    righteousness and righteousness leads to Paradise. A man may continue to 
    tell the truth and endeavour to be truthful until he is recorded with Allaah 
    as a speaker of truth. And beware of lying, for lying leads to wickedness 
    and wickedness leads to Hell. A man may continue to tell lies and endeavour 
    to tell lies, until he is recorded with Allaah as a liar.” 

    Rather people cite the riddle mentioned in the question to 
    refer to the Jews and Christians. The Jews said that the Christians follow 
    nothing, and they told the truth but they entered Hell. And the Christians 
    said that the Jews follow nothing, and they told the truth but they entered 
    Hell. 

    They narrate this from the Sufi Abu Yazeed al-Bastaami in the 
    famous story in which some of the Christians asked him this question and he 
    gave them this answer, quoting as evidence the verse in which Allah says 
    (interpretation of the meaning): 

    “The Jews said that the Christians follow nothing (i.e. 
    are not on the right religion); and the Christians said that the Jews follow 
    nothing (i.e. are not on the right religion); though they both recite the 
    Scripture. Like unto their word, said (the pagans) who know not. Allaah will 
    judge between them on the Day of Resurrection about that wherein they have 
    been differing”

    [al-Baqarah 2:113]. 

    It may also be said that this applies to the kuffaar of whom 
    Allah said (interpretation of the meaning):

    “And verily, if you ask them: ‘Who created the heavens and 
    the earth? Surely, they will say: ‘Allaah (has created them)’”

    [al-Zumar 39:38]

    and

    “Say: ‘In Whose Hand is the sovereignty of everything 
    (i.e. treasures of everything)? And He protects (all), while against Whom 
    there is no protector (i.e. if Allaah saves anyone, none can punish or harm 
    him; and if Allaah punishes or harms anyone, none can save him), if you 
    know?’ 

    89. They will say: ‘(All that belongs) to Allaah.’ Say: 
    ‘How then are you deceived and turn away from the truth?’”

    [al-Mu’minoon 23:88, 89]. 

    And there any many similar examples. Some of the kuffaar may 
    speak the truth in some of the things they say, but they will enter Hell 
    because of their kufr, not because of their speaking the truth. 

    Whatever the case, it is not appropriate to say things such 
    as this, because some people may understand from it that these people will 
    enter Hell because of the truth they speak, but this is undoubtedly false. 
    Allaah says (interpretation of the meaning):

    “Allaah will say: ‘This is a Day on which the truthful 
    will profit from their truth: theirs are Gardens under which rivers flow (in 
    Paradise) — they shall abide therein forever. Allaah is pleased with them 
    and they with Him. That is the great success (Paradise)’”

    [al-Maa’idah 5:119].