If your brother has become poor, and his hand can't support him among you; then you shall uphold him. He shall live with you like an alien and a temporary resident...
The Ohr Hachaim explains this possuk as referring to the Neshama inside each person. The person’s life’s spirit and soul become poor and weak through a lack of studying Torah and Mitzvos. The reason for this poor spirit is עִמָׁךְ – with you. If the person’s Neshama would not be attached to a person’s body, it would soar unfettered. The natural light of a human soul can illuminate the entire cosmos. The force holding it back is the human body, which darkens the light of spirituality through its physical desires.
When this happens, the soul wishes to leave the body and return to its maker. The Gemara says that a person is exhorted at birth to return his soul to his creator as he received it, with no stains or handicaps. The source for this is this possuk, that says that a person should support his life spirit and strengthen it. He should not allow his body to dim the light of his Neshama.
If he has impoverished his soul, through misdeeds and a lack of Mitzvos - וְכִי יָׁמוּךְ אָׁחִיךָ, He should do Teshuva as soon as he can and return to the correct path - וְהֶח זַקְתָׁ בוֹ. If a person does Teshuva, he will find himself back where he began, and his Neshama will be strengthened.
The Torah continues גֵׁר וְתוֹשָׁב וָׁחַי עִמָׁךְ – He shall live with you like an alien and a temporary resident. This alludes to an esoteric idea of the Torah. There are occasions when another soul attaches itself to a person’s soul. This is a kind of pregnancy, where one body carries another, and is referred to as sod ha’ibbur – the secret of pregnancy. Sometimes, this soul will attach itself to someone while he is performing a certain Mitzvah, in order to partner in this Mitzvah and merit its reward. Sometimes, it joins a person for another reason that we are not privy to. This is always a temporary thing, not a permanent Neshama switch.
The Torah now refers to both of them as גֵׁר וְתוֹשָׁב – a stranger and a sojourner. These are two types of souls that can attach themselves to a person when he encourages himself to do Teshuva and strengthen his Neshama. These two will וָׁחַי עִמָׁךְ – live with you. They are to live through you by meriting a connection to your Mitzvah.
The Torah, therefore, continues אַל תִקַח מֵׁאִתוֹ נֶשֶךְ וְתַרְ בִית וְיָׁרֵׁאתָׁ מֵׁא לוקיךָ – do not take from him anything that is his, i.e., do not cause him to lose his spiritual level because of its connection to you. Do not dim its light, and do not sully its purity by doing the Mitzvah without complete thought or attention to detail.
A person needs to fear Hashem, whose light it is that is shining through these holy souls. Not only do we have to be careful not to sully those souls, but we are exhorted to increase their light and life by וְחֵׁי אָׁחִיךָ עִמָׁךְ – your brother living with you. You are to add life to that soul, by doing extra Mitzvos and refraining from the slightest sin.
