Imaam Barbahaaree (rahimahullaah) said that Abul Aaliyah (rahimahullaah) said: ‘
Whoever dies unknown upon the Sunnah is indeed a truthful witness. It is said clinging to the Sunnah is salvation’
Shaikh Saaleh al Fawzaan commented on the above saying: The Siddeeq (the truthful one) is the one given to much truthfulness and his status is at a level after that of the Prophets. So the station of Truthfulness is a lofty station and what is intended by it is adherence to truthfulness in speech and action. The Prophet (sallal-laahu-alayhi-wasallam) made known who the Truthful One is by saying: ‘A man keeps on telling the truth until he becomes a Truthful Person’
He (i.e. the siddeeq) is truthful himself and is eager for truthfulness regarding what the people relate to him. He does not go along with everything he hears or whatever is said, rather he verifies and is eager for truthfulness because he is a truthful person. He neither narrates nor utter except the truth. This is the Siddeeq (The Truthful One).
And concerning the statement: ‘whoever dies upon the Sunnah.’
Shaikh Saaleh Al-Fawzaan comments saying: That is to cling to Islaam and what is intended by As-Sunnah is ‘Islaam’. Islaam is the Sunnah and whoever dies upon it Unknown and there appeared nothing from him in opposition to (that), then indeed he dies as a truthful person.
And concerning his statement: ‘Clinging to the Sunnah is Salvation’; that is: clinging to the Sunnah is safety from Fitan and Punishment, and for this reason he (sallal-laahu-alayhi-wasallam) said: ‘whosoever lives amongst you will see lots of differences, so stick to my Sunnah and the Sunnah of the Rightly Guided Khulafaa.’
Allaah (The Most High) said:
وَاعْتَصِمُوا بِحَبْلِ اللَّهِ جَمِيعًا وَلَا تَفَرَّقُوا
‘And hold fast, all of you together, to the Rope of Allaah, and be not divided among yourselves’[3:103]
And Allaah (The Most High) said:
وَأَنَّ هَٰذَا صِرَاطِي مُسْتَقِيمًا فَاتَّبِعُوهُ ۖ وَلَا تَتَّبِعُوا السُّبُلَ فَتَفَرَّقَ بِكُمْ عَن سَبِيلِهِ
‘And verily, this is my Straight Path, so follow it, and follow not (other) paths, for they will separate you away from His Path.’ [6:153]
This is the advice of Allah and that of His Messenger (sallal-laahu-alayhi-wasallam), and that is to adhere and cling to Sunnah.
[Source: It’haaful Qaaree Bitta’liqaat Alaa Sharhis Sunnah Lil Imaam Barbahaaree (rahimahullaah), Vol:2 page:313-314]