How does one purify a garment from urine drops after they have ceased, and is it sufficient to sprinkle water, or is it obligatory to wash with water and soap? Is it necessary to change underwear after every prayer for someone who finds it difficult to wash them outside the home?

Whoever ascertains that drops of urine have fallen on his garment, it is sufficient for him to pour water over the spot of urine until it is covered. Squeezing is not a condition according to the Shafi'is and Malikis, and it is not obligatory to use soap to remove the impurity of urine. As for someone from whom drops exit after urinating, he should take precautions by tying a piece of cloth or similar over the area to prevent the impurity from spreading to his clothes. Once the leakage of drops ceases, he should perform istinja' (ritual cleansing), then wudu' (ablution), and then pray.