In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Imaam Abdul Azeez Bin Baaz (rahimahullaah) stated about Imaam Abdur-Rahmaan As-Sadi (rahimahullaah):
He used to be a person with a lot of fiqh and concern for knowledge of the correct positions in the issues (in which) the scholars held a difference of opinion with evidence. He gave great concern to the books of Shaikhul Islaam Ibn Tamiyyah and his student Ibnul Qayyim (rahimahumallaah). He used to give preference to that which was established with evidence. He used to speak very little, except if it was in that which was beneficial. I sat with him on more than one occasion in Makkah and Riyaad–his speech was little except in the affairs of knowledge. He used to be humble and well-mannered, and whoever reads his books will know of his virtue, knowledge and great concern for (seeking) after proofs. So may Allaah shower great mercy upon him.
[For further details see: Al-Eedaahaat As-Sunniyyah Li-Usool al-Aqaa-id Ad-Deeniyyah of Al-Allaamah Zaid Bin Haadee page: 17; footnore 1]