The Mishna (55b) describes several irregular practices of the people of Jericho, some that the sages specifically objected to, while others tolerated. One custom was that they would “fold Krias Shema”, which according to some explanations, meant they would say the first sentence “Hear O Israel etc”, and the second sentence “And you shall love Hashem etc”, consecutively without inserting “Boruch Shem kvod etc”.
Since the rabbis tolerated this practice and did not openly object, the commentaries try to understand what was the beneficial quality of this practice, at least according to the people of Jericho. Shem MiShmuel (Shoftim 6) says a beautiful pshat:
In order to observe the Torah properly, one requires intellectual and emotional commitment. One without the other is incomplete. Intellectual engagement without emotional engagement leads to lack of motivation and even worse, twisted and corrupt misuse of Torah ideas for perverse ends. Emotional engagement without guidance of the intellect can lead to unfocused non-disciplined spirituality, which might abrogate the law. This dyad is represented in the first two sentences of the Shema. The first sentence is the intellectual realization of G-d and the acceptance of his authority. The second sentence is about loving G-d and emotional commitment. The people of Jericho saw fit to bind these verses together, consecutively without interruption, to reinforce this idea. The rabbis agreed with this concept however believed that actually pausing between each verse was the better way to reinforce this idea by implying that the process required two distinct forms of engagement.
The Shem MiShmuel observes further that thus dyad is also represented within the two tefilin boxes, with one on the head and one on the heart. Furthermore, the halakhic requirement that there be no delay between the tying of the Shel Rosh and of the Shel Yad indicates this idea as well. The intellect and the emotions must be united in order to properly fulfill the Torah.
Translations Courtesy of Sefaria