The phrase al-ḥasana and al-sayyia has been interpreted in five senses:
1. By al-ḥasana, victory and spoils of war are meant; by al-sayyia, killing and defeat are intended. This is the meaning in the following verses:
If a ḥasana (that is, a naṣr—victory and spoils of war, as on the Day of Badr) touches you, it distresses them; but if a sayyia (that is, killing and defeat, as on the Day of Uhud) befalls you, they rejoice at it. (Āl ʿImrān 3:120)
If a ḥasana (that is, naṣr—victory and spoils of war) befalls them, they say, "This is from Allah." But if a sayyia (that is, killing and defeat, as on the Day of Uhud) befalls them, they say, "This is from you." (al-Nisāʾ 4:78)
If a ḥasana [good] (that is, naṣr—victory and spoils of war) befalls you, it distresses them. But if a sayyia [evil] (that is, killing and defeat) befalls you... (al-Tawba 9:50)
2. By al-ḥasana, tawḥid (the oneness of God) is meant; by al-sayyia, shirk (associating partners with God) is intended, as in the following verses:
Whoever comes with a ḥasana (that is, with tawḥid), he will have better than it (that is, he will obtain good because of it [tawḥid]). And they will be safe from terror that Day. But whoever comes with a sayyia (that is, shirk), their faces will be dragged in the Fire... (al-Naml 27:89-90)
A similar usage is also found in the surahs al-Qaṣaṣ and al-Anʿām.
3. By al-ḥasana, rain and abundance of crops are meant; by al-sayyia, the lack or absence of rain, crops, and good is intended, as in the following verses:
If a ḥasana (that is, rain, abundance of crops and good) came to them, they would say, "This is our due." But if a sayyia (that is, lack of rain/drought and scarcity of crops) befell them, they would attribute it to the ill omen of Mūsā and those with him. (al-Aʿrāf 7:131)
Then We replaced the sayyia (that is, lack of rain/drought, scarcity of good and crops) with ḥasana (that is, rain and abundance of crops). (al-Aʿrāf 7:95)
We tested them with both ḥasana (that is, rain and abundance of crops) and sayyia (that is, scarcity of rain and crops). (al-Aʿrāf 7:168)
When, because of what their hands have sent forth, a sayyia (that is, lack of rain/drought) befalls them... (al-Rūm 30:36)
4. By al-sayyia, punishment in this world is meant; by al-ḥasana, the final outcome is intended, as in the following verse:
They ask you to hasten the sayyia (that is, punishment in this world) before the ḥasana (that is, before the final outcome). (al-Raʿd 13:6)
5. Al-ḥasana is used in the sense of pardon and good speech; al-sayyia, in the sense of vile/ugly speech and harm, as in the following verses:
They repel the sayyia (that is, evil speech and harm) with ḥasana (that is, good speech and pardon). (al-Qaṣaṣ 28:54)
The ḥasana (that is, pardon and forbearance) and the sayyia (that is, evil speech and harm) are not equal. (Fussilat 41:34)
Repel the sayyia (that is, evil speech and harm) with that which is best [aḥsan] (that is, pardon and forbearance). (al-Muʾminūn 23:96)
A similar usage is also found in the surah al-Raʿd.