68:8 When a traveler prays the morning service, he should be sure to put on his tallis the same way that he would in his shul at home because the tallis katan (i.e., his tzitzis) is far from the necessary size. If one is traveling on foot, he must stand in place to recite the verse of Shema and “Baruch Shem…” with proper concentration. (Some authorities require this through the words “al levavecha” – Mishnah Brurah 63:11.) If he is riding on an animal or traveling in a wagon, he may recite Shema without stopping but he must still stand in order to recite Shemoneh Esrei. (Mishnah Brurah 63:10 requires a rider to stop for Shema and “Baruch Shem…”.) If one’s journey is urgent, he should stand in place for at least the first three and last three blessings of Shemoneh Esrei but if this is not possible, he may daven while seated, and even bow in a seated position. (He should turn his face towards Jerusalem if possible – MB 94:15.) It is better, however, to recite Shemoneh Esrei at daybreak before his journey begins (even though this is earlier than optimum). Similarly, mincha (the afternoon service) should be said a half an hour after midday (likewise earlier than usually suggested) if this will enable one to daven standing. One must go back a mil (about 2/3 mile) to get water to wash his hands for prayer or to be able to daven with a minyan as per 12:5 and 12:8.
68:9 Previously discussed laws: If a traveler has no water to wash for bread, see 40:14; that one who has eaten bread may not leave until after bentching (grace after meals), see 42:19; that bentching must be recited sitting, see 44:6. However, if one ate while traveling on the road, he may also bentch while traveling. The reason for this is that his anxiety about resuming his journey will spoil his concentration. Nevertheless, if he sat to eat, he must also sit to bentch.