What is the ruling on performing ablution with rainwater collected before it reaches the ground, and is it permissible to perform ablution with pure water (purified) by means of water desalination machines?

It is permissible to perform ablution with rainwater because it is absolute water, as indicated by verse 11 of Surat Al-Anfal: "And He sends down upon you from the sky water to purify you with it." Al-Shirazi, in Al-Muhadhdhab, and Kashshaf Al-Qina' concurred on the permissibility of removing ritual impurity (hadath) and physical impurity (najas) with absolute water such as rain, snow, and hail. As for purified water, purification with it is permissible if the trace of impurity (color, taste, and smell) has been removed from it. This was affirmed by the Council of Senior Scholars in the Kingdom of Saudi Arabia, stating that it is permissible to use it for removing ritual impurities and physical impurities and for achieving purity, as long as there is no health harm from its use.