Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says that this verse: "Then indeed your Lord, to those who emigrated after they had been put to trial, then strove and were patient - indeed your Lord, after that, is Forgiving and Merciful" [Surah al-Nahl: 110], was revealed concerning those companions of the Prophet (peace and blessings be upon him) who were made targets of oppression and persecution in Makkah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17757