Sheikh `Abd al-Qadir al-Jilani clarifies the importance of going beyond the bare minimum in an allegory he mentions in Ghunya li Talibi Tariq al-Haqq. Hanbalis sometimes mention it in their books-but without attribution to Sheikh `Abd al-Qadir. One of these is al-Saffarini's Ghudha al-Albab, a commentary on general refined behavior (adab). The translation appears below, with the original Arabic following:
The allegory of belief [iman] is that of a land that has five walls.
Al-Hajjawi said in its commentary: It is said that the allegory of belief
is that of a land that has five walls. The first wall [the innermost wall]
made from gold, the second from silver, the third from iron, the forth from
cooked clay [aajurr], and the fifth [the outermost wall] from brick. As
long as the people of the brick wall are diligent in protecting the brick,
the enemy does not aspire [destroying] the second; but if they neglect this
[brick wall], they will aspire for the second and then the third, until
they demolish all of the walls. And like belief [iman] has five walls:
certainty, then sincerity, then performing what is obligatory, then the
recommended [sunan], and then refined behavior [aadab]. As long as one
holds to and is diligent with having refined behavior, Satan does not
scheme [to destroy] him. But if one forsakes refined behavior, Satan
aspires to [destroying] the recommended works, then the obligatory, then
sincerity, and then certainty.
[Source: Al-Saffarini, Ghudha al-Albab. 1:27]
And Allah knows best.