In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
There is no performance of Istinjaa for passing wind, rather Istinjaa is (performed after) urination and defecation. It is not legislated for the one who passes wind to perform Istinjaa before performing ablution as some people do; because (performance) of Istinjaa for passing wind has not been transmitted in the legislated Islamic proofs; rather the passing of wind is a ritual impurity requiring the (performance) of ablution. And all praise be to Allaah for His facilitation of ease. Imaam Ahmad (rahimahullaah) said: (The performance) of Istinjaa due to passing wind is neither (legislated) in the Qur’aan nor in the Sunnah, rather what is obligatory is performance of ablution. [Source: Al-Mindhaar Fee Bayaani Katheer Minal Akhtaa Ash-shaa-i-a; page:23. By Shaikh Saaleh Aala Ash-Shaikh (hafidhahullaah)]