גַּ֛ם אִם־יִשְׁכְּב֥וּ שְׁנַ֖יִם וְחַ֣ם לָהֶ֑ם וּלְאֶחָ֖ד אֵ֥יךְ יֵחָֽם׃
דאָס גלײַכן אַז צװײ ליגן באַנאַנד, איז זײ װאַרעם, אָבער אײנעם װי קען װאַרעם װערן?
Tze'enah Ure'enah
“Also” [4:11]. Also, when two sleep next to each other, they keep each other warm, but one cannot warm himself.
Rashi
They can be warm. [To be understood] according to its apparent meaning, regarding male and female, who are aroused by one another and procreate.16Alternatively, these verses refers to the performance of a mitzvah, i.e., if each one performs a mitzvah on his own then if he slackens off, there is no one to encourage him and “uplift him.” However, when two people perform a mitzvah together, it adds “warmth” to their performance of the mitzvah. (Divrei Avrohom)