God Kabir Ji (Kavir Dev) gave Satnaam to Guru Nanak Dev Ji and showed him Satlok (Sachkhand)
Source: www.jagatgururampalji.org

Shri Nanak Dev Ji previously used to do jaap of one Omkaar (Om') mantra and only considering it to be true used to say ‘Ek Omkaar’. Kabir Sahib appeared before Shri Nanak Dev Ji on the bank of river Bein and took him to Satlok (Sachkhand) and showed him His SatPurush form and then on the third day left him back on the Earth. After that Shri Nanak Ji eulogised the eye-witnessed glory of God Kabir, which is present in his sacred speech in Shri Guru Granth Sahib in Mehla Pehla. Only after God Kabir gave Shri Nanak Ji jaap of Satnaam, Shri Nanak Ji got liberated from Kaal’s lok.

Rag “Siri” Mehla 1, page no 24, Shabd no.29

Ek suaan duii suaani naal, bhalke bhaunkahi sadaa biaal
Kud chhura mutha murdaar, Dhaanak roop raha Kartaar
Mai pati ki pandi na karni ki kaar, uh bigdae roop raha bikraal
Tera ek naam tare sansaar, main eha aas eho aadhaar
Mukh ninda aakha din raat, par ghar johi neech manaati
Kaam krodh tan vasah chandaal, Dhaanak roop raha kartaar
Faahi surat malooki ves, uh thagvaada thagi des
Kharaa siaana bahuta bhaar, Dhaanak roop raha Kartaar
Main keeta na jaata huraamkh or, uh kia muh desa dusht chor
Nanak neech kah bichaar, Dhaanak roop raha Kartaar

It has been clearly written in this that one dog (in the form of mind) and along with these two bitches (in the form of expectations and desires) are always unnecessarily barking (i.e. desires keep on arising) and new-new expectations keep arising all the time. The method (without Satnaam) of killing them was a false (kud) means (muth murdaar). God (Kabir Sahib) met me in the form of a weaver (dhaanak). He told me the correct way of worship.

Shri Nanak Sahib Ji says that without the sadhna of that God (Dhaanak / weaver Kabir Sahib) neither there would have been any reputation (pati) nor there was any good deed (good earning) being done. Consequently, the terrible form of Kaal which I have perceived now, Kabir Sahib, from that only your one (Satnaam) naam can convey the whole world across (can extricate from Kaal’s lok). Even I (Nanak Ji says) am only hopeful of your this naam, and only this naam is my base. Earlier I must have also criticised you a lot out of ignorance because lust and anger, these devils live in this body.

The God in the form of a (dhaanak) weaver (Kabir Sahib who used to work as a weaver) came and showed me the true path and released me from Kaal. His (surati) appearance is very pleasing and charming and is in beautiful attire (in form of Jinda). He met me; nobody can recognise Him, who even befooled Kaal i.e. He appears to be a dhaanak (weaver) and then became Jinda. Even Kaal God became confused that this is someone of a low caste; he can not be God (Purna Brahm). In this way, Kabir Sahib hiding his real form comes as a servant. Kaal or an ordinary person cannot recognise Him. Therefore, Shri Nanak Sahib Ji has called him a thug (imposter) and along with this has said that Dhaanak (weaver Kabir Sahib) is very intelligent. Appears to be something else, but is very magnificent (bahuta bhaar), the God Purna Brahm who has Himself come in the form of a weaver, a dhaanak. To instruct every human being on submissiveness, accepting his mistake says that I (Nanak Ji) argued with Purna Brahm and He (Kabir Sahib) also presented Himself (acting) as a servant and addressed me (Nanak Ji) as Master. Therefore highlighting His greatness and repenting on his ignorance Shri Nanak Ji says that I (Nanak Ji) was not even worthy of doing and getting anything done. Even then considering my sadhna to be superior, confronted (debated on knowledge) God. Who can be as low, wicked and good-for-nothing like me, who could not recognise his Lord-Master Purna Parmatma in a dhaanak form (Supreme God Kabir Sahib who came as a weaver)? Shri Nanak Sahib Ji states that I am saying all this with full consideration that the Supreme God is in the form of a dhaanak (Weaver Kabir).

Rag "Tilang" Mehla 1, Page 721

Yak arj guftam pesh to dar gosh Kun Kartaar l Hakka Kabir kareem tu beaeb Parvardagaar ll

Duniyaan mukaame faani tahkeek dildaani l Mm sar mui ajraail giraft dil hech na daani ll

Jan pisar padar biraadraan kas nest dastM geer l Aakhir byaftam kas nadaarad choon shabd takbeer ll

Shabroj gashtam darhawa kardem badi khyaal l Gaahe na neki kaar kardam mm ii cheeni ahwaal ll

Badbakht hum chu bakheel gaafil benazar bebaak l Nanak bugoyad janu tura tere chaakra paakhaak ll

Meaning:

Oh Creator, the Master, the unqualified Saint, kind “Sat Kabir” (Eternal Kabir), You are flawless God. There is a request before you from the heart that of Beloved, this residence of world is destructible. I have realised this completely. Oh benefactor, on death of this living being, a messenger of Yam named Ajrail, capturing mercilessly takes him away. No companion like, son, father, relative gives company. In the end, all the schemes, obligations, and rituals/actions are of no use. Everyday, evil thoughts like non-stop blowing wind keep patrolling. I did not get any means of doing meritorious acts. In such a bad time, Kaliyug, the ignorant and careless like us, because of not having knowledge of the true path, were blind and dumb. Nanak, the dust of the feet of the servant of your servants, the drowning man got across.

Read full account on Kabir Sahib and Guru Nanak Dev Ji