The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) in Parashat Nisavim discusses methods of purification. The best way is immersing in a Mikveh containing 40 Se’ah. However, if one is unable to use a Mikveh, he presents an alternative: Netilat Yadayim (washing the hands) forty times.
The first step is to wash once on the right and then once on the left, with Kavana (intent) on the first letter of the divine name of seventy two. This refers to the YKVK (Tetragrammaton) spelled out with the letter Yud, which equal 72 in Gematria. (Listen to audio for detailed explanation). This formulation of the Divine name contains ten letters: YUD-HY-VYV-HY. He continues to wash each hand, right and then left, focusing on the next letter in the sequence. At this point, he has washed his hands twenty times. Next he washes ten times on the right hand, thinking of all ten letters. Then he washes ten times on the left, thinking again of all ten letters.
[Listen to Audio for allusion in the letters of the word ShOFaR to Teshuba in general and specifically to purifying oneself from transgressions connected with Kedushat HaBrit (holiness of the covenant).]
Rabbenu Yonah quotes the Rambam who said that since his youth, he never missed a day of praying with purity. This important teaching of the Ben Ish Hai enables one to purify himself from Tuma’at Keri (the impurity of seminal emission) and pray with purity, even if he cannot immerse in a Mikveh.