First,  let's know which all tīrtha-sthala constitute pañca-kedāra (literally - the five kedaras).

>  1. Kedāranātha (केदारनाथ) 
>  2. Madhyamaheśvara (मध्यमहेश्वर) or Madamaheśvara (मदमहेश्वर) 
>  3. Tunganātha (तुङ्गनाथ) 
>  4. Rudranāth (रुद्रनाथ) or Mahālaya (महालय) 
>  5. Kalpeśvara (कल्पेश्वर)

The popular local/folkloric legend<sup>**1**</sup> associated with these pañca-kedāras is as follows:-

> The legend goes that Lord Shiva was hiding from the Pandavas by taking
> the form of a buffalo but was identified by Bhima, one of the five
> Pandava brothers. On being recognised, the deity disappeared and
> manifested himself in five different locations in the Himalayas. **It is
> said the each of these sites is dedicated to a part of the Lord -
> Kedarnath (the hump of Lord Shiva), Madhmaheshwar (His belly button),
> Tungnath (His arms), Rudranath (His face), Kalpeshwar (His jata or
> hair).**
>
> Taken from Uttarakhand government [e-tourism site][1]. 



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Now, 

As far as I could research, the notion of collectively referring the above five shrines of Śiva as pañca-kedāra is not found in any currently published and/or extant canonical texts, which have pan-Hindu appeal. 

However, since this is from Uttarakhand, there's a popular notion of this, and a local text named  Kedār - kalpa, which claims to be a part of kedāra khaṇḍa of Skanda Purāṇa, mention this. Most probably it's a shala-purāṇa recension of Skanda Purāṇa's kedāra khaṇḍa, but we cannot be sure, as I ask about same in [this question](https://hinduism.stackexchange.com/questions/50460/what-is-kedar-kalpa). 

In any case, here's the reference to pañca-kedāra found in [Kedara kalpa](https://archive.org/details/SkandaPuranaWithRatnaPrabhaHindiTikaOfBrajRatnaBhattachrya1906VenkateshwarPress/page/n313/mode/1up?view=theater):

> पट्पञ्चाशोऽध्यायः ५६.<br><br> ईश्वर उवाच॥<br> **पंच स्थानानि देवेशि
> कथितानि तवानघे॥केदार मध्यमं तुंगं कल्पेश्वरमहालयम्** ॥ १॥ <br>**पंच
> तीर्थानि यो देवि गच्छति भक्तिसंयुतः ॥** प्रसंगाडा
> बलात्काराज्ज्ञानादज्ञानतोपि वा ॥२॥ <br>न वै तत्सदृशो देवि पुण्यात्मा
> नात्र संशयः ॥ तस्य दर्शनमात्रेण पूताः स्युः पापयोनयः॥३॥
> <br>ब्रह्माद्या लोकपालाश्च ते नमंति महेश्वरि ॥ इह चापि वरान् भोगान्
> मृतो मोक्षमवाप्नुयात् ॥४॥<br>**पंचकेदारमाहात्म्यं शृणुयायः समाहितः ॥**
> <br>सर्वतीर्थेषु स स्नातः पूजिताः सकलाः सुराः ॥ <br> यद्यदिच्छति
> तत्सर्व प्राप्नोति गिरिनंदिनि ॥५॥<br> प्रातः स्मरति यो नित्यं
> तीर्थानां पंचकं शुभम् ॥ सर्वपापविनिर्मुक्तः स गच्छति परां गतिम् ॥६॥
> <br>इति ते कथितं देवि किमन्यच्छ्रोतुमिच्छसि ॥७॥ <br>इति श्रीस्कांदे
> केदारखंडे कैलासमाहात्म्ये पंचकेदारमाहात्म्यं नाम पटपंचाशोऽध्यायः ॥५६॥
> 
> <sup>
> 
>> यद्यदि महादेवजी बोले-हे निष्पापदेवेश्वार ! **पांच क्षेत्रोंका हमने
> तुम्हारे प्रति वर्णन कि केदार, मध्यम, तुङ्ग, कल्पेश्वर और महालय ॥ १॥
> भक्तिपूर्वक जो पुरुष इन पांच क्षेत्र की यात्रा करताहै,** अथवा किसी
> प्रसंगसे, वरजोरी, ज्ञान वा अज्ञानसेभी यात्रा करताहै ॥२ | निःसन्देह
> उसकी बरावर और कोई पुण्यात्मा नहींहै, उसके दर्शन करनेसे बडे २ पायी
> पवित्र होजातेहैं ॥ ३ ॥ हे महेश्वरि ! ब्रह्माआदि सब देवताभी वहां आय २
> कर नमक | करतह, उस स्थानके दर्शन करनेवाला व्यक्ति इस संसारमें अनेक
> प्रकारके शुभ भोगोंको । गता आर मरकर मोक्षलाभ करताहै ॥ ४ ॥ **चित्तको
> एकाग्र करके जो व्यक्ति पंचकेदार माहात्म्यका श्रवण करताहै, मानो उसने
> सबै तीर्थों में सान करलिया और संपूर्ण देवता पूजा करली ।** विशेष क्या हे
> गिरिनन्दिनी ! वोह व्यक्ति जिस २ वस्तुकी कामना करताहै । सभी उसे प्राप्त
> होताहैं ॥ ५ ॥ जो पुरुष नित्य मातःसमय इन शुभ पांचों तीर्थोंका स्मरण
> करताहै. वोह व्यक्ति समस्त पापोंसे मुक्तहो परम गतिका लाभ होताहै ॥ ६॥ हे
> देवि यह तौ सब कुछ हमने तुम्हारे प्रति वर्णन किया अब और क्या श्रवण
> करनेकी तुम्हारी इच्छाहै ॥७॥ इति श्रीस्कांदे केदारखण्डे भाषाटीकायां
> षट्पञ्चाशोऽध्यायः ॥ ५६
> 
> </sup>
>
> 
>
> Paṇḍita Brajaratna Bhaṭṭācāryya kṛta Ratnaprabhā Hindī ṭīkā on Kedāra Kalpa.
>
>> Bhagavāna Śiva said:-O Pious goddess! Thus, **I described the fives shrines viz. Kedāranātha, Madhyamaheśvara, Tunganātha, Kalpeśvara, Mahālaya (Rudranāth).** Whoever visits these shrines with devotion, even so unwillingly or without motif, there's no soul more Pious than that, sanctifying even the worst of sinners. O Maheśvarī! All Devas including Brahmā, visit these tīrthas. Just by visiting these shrines one becomes liberated. **If someone listens to the glory of these five shrines (pañca-kedāra) with complete devotion and attention, that becomes equivalent to have traveled and bathed in all tirthas**. Such a person acquires whatever he desires. The one who remembers these five holy shrines in the morning becomes free of all sins and attains Supreme abode. 
Thus, ends glory of Pañca-Kedāras. 
>
> `English Translation of the Hindi Translation by Self.`


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**[1\]:** Something very similar, although, can be found in [Verse 3 to 7 from Adhyaya 52][2] of kedāra-kalpa. So this cannot be totally considered as a folk tale. 


  [1]: https://uttarakhandtourism.gov.in/panch-kedar
  [2]: https://archive.org/details/SkandaPuranaWithRatnaPrabhaHindiTikaOfBrajRatnaBhattachrya1906VenkateshwarPress/page/n290/mode/1up?view=theater