It was said to Al-Hasan Al-Basri (rahimahullaah): Indeed, the people say that ”Whoever testifies that none has the right to be worshipped except Allaah will enter paradise”; so he (i.e. Al-Hasan) said: ”Whoever testifies that none has the right to worshipped except Allaah and then he fulfills its rights and obligations, he will enter paradise”. [Jaami-ul Uloom Wal-Hikam: 224]

It was said to Al-Wahb Ibn Munabbih (rahimahullaah): ”Is not the testimony that ‘none has the right to be worshipped except Alllaah’ the key to paradise? He said: ‘Certainly, but there is not a key except that it has teeth; so if you come with a key that has teeth, it will open for you, otherwise it will not open for you.’ [Jaami-ul Uloom Wal-Hikam: page:224]