2/224-227 — The oath: a word used as an excuse
"Do not make God a shield for your oaths, so as to be kept from doing good, from guarding yourselves and from setting things right between people…"
عُرْضَة — root ع-ر-ض: what lies crosswise, what is set in front. The lexicographers give here the senses "an obstacle placed in between" and "an excuse constantly put forward". The oath, that is, turns into a pretext put forward for not doing what ought to be done.
The situation the verse points to is concrete: in anger a person says "I swear I will never speak to him again"; then, when reconciliation is called for, he offers his oath as a ground. The verse does away with this use of the oath.
لَّا يُؤَاخِذُكُمُ ٱللَّهُ بِٱللَّغْوِ فِىٓ أَيْمَٰنِكُمْ — "you are not held answerable for the laghw in your oaths."
The root ل-غ-و was analysed in the section on al-Wāqiʿa 56/25: a word not counted, that goes for nothing. Here the word is used as a legal term: an oath that comes out of the mouth without being intended.
And the measure is given at once: bimā kasabat qulūbukum — what the hearts have earned. The measure, that is, is not the wording but the intention.
ٱلَّذِينَ يُؤْلُونَ مِن نِّسَآئِهِمْ تَرَبُّصُ أَرْبَعَةِ أَشْهُرٍ — īlāʾ: to swear not to approach one's wife. In the age of ignorance this was used to leave a woman in an indefinite uncertainty: neither married nor divorced.
What the verse does is to set a term: four months. After that there are two roads, and both are named in the verse: to return (fāʾū) or to divorce (ʿazamu'l-ṭalāq).
The uncertainty, that is, is removed. This is the working seen again and again in this section of the sūra: a practice is not forbidden, its being without a term is forbidden.