The brothers of Yosef stood at an incredibly high spiritual level. As the Ramban notes, they were so holy that their names were inscribed on the High Priest's breastplate (Choshen Mishpat) - a testament to their spiritual greatness. Yet, even they demonstrated this fundamental principle about falsehood - it inherently creates a barrier to spirituality which cannot be focused on when engaged in falsehood. Namely, when the brothers lied to Yaakov about Yosef’s death, their message to him was devoid of any spiritual details (e.g. the brothers could have told Yaakov that they came upon Yosef while he was learning and saw that an animal had attacked him). The fact that there were no spiritual details in their accounting of what happened to Yosef, gave Yaakov pause (and hope) that perhaps the brothers may have been lying and Yosef was still alive.
With this in mind, we have a deeper understanding of why Yosef, when he wished to convey to Yaakov later in the Parsha that he was still alive, used a sign that relates to spirituality, namely he sent wagons to signal to Yaakov that he remembered the last thing that Yaakov and Yosef learned together (which were the Halachos of Eglah Arufah – the decapitated heifer). As the GRA explains (as cited in the Kaftor VaFerach): "And when Yaakov saw the sign of holiness, he understood that this time the words were true." As we have stated, Yaakov believed that it was true that Yosef was still alive, because had it been a lie, the message could not have contained details of spirituality, i.e. what Yaakov and Yosef had been learning.
This is an important lesson for all of us to internalize. If we are involved in falsehood, it creates a barrier that precludes us from focusing on our spirituality. We cannot compartmentalize this and comfort ourselves by thinking that we are still good people focused on our spiritual growth, if at the same time we act dishonestly or unethically in our everyday affairs.
