Menachot 35b

Whenever a man puts on his tefillin he must recite the benediction: so Rabbi;

but the Sages ruled, He recites the benediction in the morning only.

It was stated: Abaye ruled, The law is in agreement with Rabbi, while Raba ruled, The law is in agreement with the Rabbis.

R. Mari the son of Samuel's daughter remarked, I noticed that Raba himself did not act in accordance with his own ruling but rising early, he would go to the privy, emerge and wash his hands, put on his tefillin and recite the benediction, and when he had to attend to his needs a second time he would go to the privy, emerge and wash his hands, put on his tefillin and recite the benediction again.

Mar Zutra remarked, I notice that R. Papa recited the benediction whenever he put on his tefillin.

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.

R. Hisda said, If a man spoke between the putting on of the [hand] tefillah and the [head] tefillah, he must make another blessing.

[Evidently] only if he spoke, he must [make another blessing], but not if he did not speak.

But R. Hiyya the son of R. Huna sent [from Palestine] the following decision in the name of R. Yochanan: Over the hand-tefillah one must say, ‘Blessed [are You, O Lord our God, King of the universe,] who has sanctified us with your commandments and has commanded us to put on the tefillin.'

Over the head-tefillah one must say, Blessed . . . who has sanctified us with your commandments and has commanded us concerning the precept of the tefillin!'

Abaye and Raba both said, It means, if he did not speak [between one tefillah and the other] he must only recite one blessing, but if he did speak he must recite the two blessings.

One taught: When a man puts on the tefillin, he should put on first the hand-tefillah and then the head-tefillah, and when he takes them off, he should take off first the head-tefillah and then the hand-tefillah.

Now it is right that when he puts them on he should put on first the one on the hand and then the one on the head, since it is written, "And you will bind them for a sign upon your hand, and then it says, And they shall be for symbols between your eyes;"

but from where do we know that on taking them off he should first take off the one from the head and then the one from the hand?

Rabbah said, R. Huna explained it to me. The verse says, "They shall be for symbols between your eyes," that is to say, so long as they are ‘between your eyes' both shall be there.