Is it obligatory to change one's position for istinja' (cleaning oneself after relieving oneself)?

The Shaykh : Moving from one's position is also not a recommended practice (sunnah). One should perform istinja' in the place where he relieved himself, and there is no need to move. If he does move, he will either hold his penis with his hand, which will contaminate the hand, or he will release it, which will contaminate his clothes and thighs. Therefore, performing istinja' in the place of urination and taking care to avoid ritual impurity (najasah) is the best course of action. Allah knows best.