Donning tefillin before a journey
Someone who must set out on a journey before the time for donning tefillin may don his tefillin without a beracha before daybreak if he is unable to put them on while travelling. Once it is light, he should adjust the tefillin and recite the beracha. If the beracha was mistakenly said at night, it is not repeated by day. This leniency applies only to those travelling by foot. Those travelling by wagon, train, car or other form of transportation in which a person can fall asleep are not permitted to put on their tefillin prior to the correct time.
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