Al-Miqdaad ibn Al-Aswad (a Companion) narrated that the Prophet of Allah, sallallaahu ‘alayhi wa sallam, said to his Companions: “What do you say regarding adultery?” They said: “Allah and His Messenger have forbidden it, so it is forbidden until the Day of Judgment.” He, sallallaahu ‘alayhi wa sallam, said: “To commit adultery with ten women is less of a sin than to commit adultery with the wife of his neighbor.
The Prophet of Allah, sallallaahu ‘alayhi wa sallam, then said: “What do you say regarding stealing?” They said: “Allah and His Messenger have forbidden it, so it is forbidden.” He, sallallaahu ‘alayhi wa sallam, said: “To steal from ten houses is less of a sin than to steal from his neighbor.”
Al-Manaawi (a scholar) said: “This is because the right of a neighbor is that he does not betray him regarding his wife. If he does so, then his punishment for that one act of adultery is more severe than ten other times with another woman.”