Lets compile qoutes from bani on the mahatam of mool manter and gurmanter.
From SGGSJM Ang 1040
ਮੂਲ ਮੰਤ੍ਰੁ ਹਰਿ ਨਾਮੁ ਰਸਾਇਣੁ ਕਹੁ ਨਾਨਕ ਪੂਰਾ ਪਾਇਆ ॥੫॥
Chanting the Mool Mantra, and the Name of the Lord, the source of nectar, says Nanak, I have found the Perfect Lord. ||5||
From SGGSJM Ang 675
ਅਉਖਧ ਮੰਤ੍ਰ ਮੂਲ ਮਨ ਏਕੈ ਮਨਿ ਬਿਸ੍ਵਾਸੁ ਪ੍ਰਭ ਧਾਰਿਆ ॥
The Mul Mantra, the Root Mantra, is the only cure for the mind; I have installed faith in God in my mind.