And do not take your oaths as [means of] deceit between you, lest a foot slip after it was [once] firm, and you would taste evil [in this world] for what [people] you diverted from the way of Allāh,1 and you would have [in the Hereafter] a great punishment.
Translation: Saheeh International (English)
1 Referring to those who would be dissuaded from Islām as a result of a Muslim's deceit and treachery.
Do not make your oaths a means of deception thereby allowing you to trick and deceive one another, following your desires - breaking them whenever you wish and fulfilling them when you wish. If you do so your feet will slip from the straight path after being firm on it. You will taste the punishment on account of your deviation from Allah’s path and your misleading others from it and you will receive multiplied punishment.