Divrei Yechezkail Shraga: Vayeitzei: Raising The Letters
“Then Jacob took a stone and raised it as a monument.” (Genesis 31:45) The Kabbalah refers to the letters of the Hebrew alpha bet as stones. A person must work at raising each stone to its source. Jacob was thus able to raise the letters and then teach his children, described as his brothers, to do the same: He taught them that they were brothers in this ability. (Divrei Yechezkail Vayeitzei)
It is difficult enough to pay attention to all the words of prayer. The Divrei Yechezkail is teaching us, that even that is insufficient: we must raise each letter by focusing our attention on every detail of our prayers