The Rabbis of the school of R. Ashi recited the benediction whenever they touched their tefillin.
R. Samuel b. Bidri said in the name of Rav (according to some, R. Aha Arika said it in the name of R. Huna, while according to others, R. Menashya said it in the name of Samuel), When must one recite the blessing over the tefillin? As soon as they have been put on.
But this cannot be, for has not Rav Judah said in the name of Samuel that with regard to all precepts the blessing must be recited prior to the performance thereof?
Abaye and Raba both said, It means, from the time they have been put on until they have been tied.
אמר עולא כל הקורא ק"ש בלא תפילין כאילו מעיד עדות שקר בעצמו א"ר חייא בר אבא א"ר יוחנן כאילו הקריב עולה בלא מנחה וזבח בלא נסכים: ואמר רבי יוחנן הרוצה שיקבל עליו עול מלכות שמים שלמה
יפנה ויטול ידיו ויניח תפילין ויקרא ק"ש ויתפלל וזו היא מלכות שמים שלמה א"ר חייא בר אבא א"ר יוחנן כל הנפנה ונוטל ידיו ומניח תפילין וקורא ק"ש ומתפלל מעלה עליו הכתוב כאלו בנה מזבח והקריב עליו קרבן דכתיב (תהלים כו, ו) ארחץ בנקיון כפי ואסובבה את מזבחך ה'
For R. Jannai said: Tefillin demand a pure body, like Elisha-the-man-of-the-wings. What does this mean? — Abaye said: That one must not pass wind while wearing them; Raba said: That one must not sleep in them. And why is he called 'the man-of-the-wings'? Because the wicked State once proclaimed a decree against Israel that whoever donned tefillin should have his brains pierced through; yet Elisha put them on and went out into the streets. A quaestor saw him: he fled before him, and the latter gave pursuit. As he overtook him, he [Elisha] removed them from his head and held them in his hand, 'What is that in your hand?' he demanded, 'The wings of a dove,' was his reply. He stretched out his hand and the wings of a dove were found therein. Hence he is called 'Elisha-the-man-of-the-wings.'