This special prayer was composed by the SheLah Hakadosh (Rabbi Isaiah ben Abraham HaLevi Horowitz) to express the prayers of parents on behalf of their children.
The SheLah Hakadosh said the optimal time for parents to recite this prayer is erev Rosh Chodesh Sivan, which this year is on Sunday May 21st. for this is the month when God gave us the Torah, and when the Jewish people began to be called His Children. However, one may recite it anytime.
On that day, the SheLah Hakadosh writes, fathers and mothers should also give tzedaka (charity) to the poor, do teshuva (repent) and fast if they are able.
As erev Rosh Chodesh is on Shabbat this year, it is customary to read this prayer today, Friday, May 19th.