What is the difference between "فأنجيناه" (So We saved him) in verse 119 of Surat Al-Shu'ara and "فنجيناه" (And We saved him) in verse 170 of the same Surah?

The words "fa anjainahu" (فَأَنْجَيْنَاهُ - so We saved him) and "najjainahu" (نَجَّيْنَاهُ - We saved him) are equivalent in meaning. The difference between them is merely a stylistic variation in wording, but the meaning is the same. This is supported by what Al-Tahir ibn Ashur mentioned in his tafsir (definition), "Al-Tahrir wa'l-Tanwir," regarding the verse: "Then We save Our Messengers and those who have believed. Thus, it is a duty upon Us to save the believers" (10:103). The difference between the two recitations (qira'at) is a stylistic variation, but the meaning is one.