Is it permissible to perform ablution and pray in clothes that have been splattered with dry urine drops?

There is a difference between praying in impure clothes and performing ablution (wudu') while wearing them. Praying in impure clothes is invalid because the purity of one's garments is a condition for the validity of prayer. These clothes must be purified or changed for prayer, regardless of whether the urine is dry or not. As for performing ablution while wearing impure clothes, this is permissible, as the purity of one's clothes is not a condition for ablution.