Shiva Purana
विहिताविहिताभेदात्तामनेकां विदुर्बुधाः ॥ तयोर्बहुविधत्वाच्च विस्तारो न हि वर्ण्यते ॥ २२॥
Learned men consider devotion to be of different sorts, such as ordained and non-ordained. Since they are of various types they are not explained in detail.
english translation
vihitAvihitAbhedAttAmanekAM vidurbudhAH ॥ tayorbahuvidhatvAcca vistAro na hi varNyate ॥ 22॥
hk transliteration by Sanscript