It is reported that ‘Abdullâh b. Mas’ûd – Allâh be pleased with him – said:
The example of the believer, the unbeliever and the hypocrite is that of three people who arrived at a valley. One of them descended and passed through to the other side. One of them descended until he reached half way, when the third man on the edge of the valley called to him, “Woe to you, where are you going? You will die. Come back.” The man who made it to the other side called to him, “Come and be saved.” So [the man in the middle of the valley] kept looking back and forth at the two [on each side of the valley], when a flood came into the valley and drowned him. The man who passed through to the other side is the believer; the one who drowned is the munâfiq (hypocrite) –
[The Hypocrites] sway between this and that, neither [fully] with the believers nor with the unbelievers. [Quran 4:143]
And the one who remained at the edge of the valley [not able to escape the flood and pass] is the kâfir (unbeliever).
Ibn Abî Hâtim, Al-Tafsîr article 6144.