In The Name of Allaah, The Most Merciful The Bestower of Mercy.
Imaam Ibnul Qayyim [rahimahullaah] said that Bishr Ibul Haarith [rahimahullaah] said: The people of the hereafter are three: The Aabid, the Zaahid and the Siddeeq. The Aabid worships Allaah [i.e. with love, fear and hope] whilst being attached to searching for [permissible] provision. The Zaahid worships Allaah [i.e. with love, fear and hope] whilst not being attached to worldly things which one can do without. The Siddeeq worships Allaah [i.e. with love, fear and hope] together with pleasure and compliance [i.e. strict compliance with Allaah’s commands and prohibitions]; he takes from the [permissible] worldly things when he sees it fit to [do so] and abandons them when he sees it fit [to do so]. [Al-Fawaa-id: page: 175. Abridged & Slightly paraphrased.]
Who is an Aabid? [A devout worshipper]
Who is a Zaahid? [He is one who abandons those permissible things he is not in need of, which also are not of any benefit to him in the afterlife. (See Madaarij As-Saalikeen). Sufyaan Ath-thawree said that the Zaahid is not the one who eats stringy food or wears woollen clothes, rather he is one who neither rejoices in some worldly gain nor becomes sad when he fails to get something.]
Who is a Siddeeq: [Shaikh Saaleh al Fawzaan says: The Siddeeq is the one who is (known) for much truthfulness and is extremely truthful. [Al-Haa-iyyah: page:117]