(Will you call upon Ba`l and forsake the Best of creators,) Ibn `Abbas, may Allah be pleased with him, Mujahid, `Ikrimah, Qatadah and As-Suddi said that the word Ba`l means lord. `Ikrimah and Qatadah said, "This is the language of the people of Yemen." According to another report from Qatadah, it is the language of Azd Shanu'ah. `Abdur-Rahman bin Zayd bin Aslam narrated from his father that it is the name of an idol which was worshipped by the people of a city called Ba`labak (Baalbek) which is to the west of Damascus. Ad-Dahhak said, "It is an idol which they used to worship."
In verse 128, it was said: إِلَّا عِبَادَ اللَّـهِ الْمُخْلَصِينَ (except the chosen servants of Allah). Here, the word used is: مُخْلَصِينَ (mukhlasin) (pronounced with a fathah on the letter lam) which means chosen, elected, people Divinely identified as special. As such, these will be people whom Allah has elected to become recipients of the honor of having obeyed Him perfectly and made themselves deserving of the best returns and rewards from Him. Hence, it would be more appropriate to translate it in the sense of 'the chosen' rather than 'sincere.'
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 122–131
God helped the Prophet Moses and his community and relieved them from the oppression of Pharaoh. This was made possible through the dawah work performed by Moses. He preached the truth before Pharaoh. After the completion of the tenure of his dawah mission came the time for Pharaoh to be pronounced guilty and to be destroyed; and for Moses and his community to be victorious and dominant. In this context, one of the meanings of ‘showing the straight path’ is that the right solution to the problem of Pharaoh was revealed to them. Though this was a problem faced at the community level, its solution nevertheless lay in communicating the divine message. So, the victory and supremacy which they achieved was the result of dawah efforts and was not due to any national struggle or rebellion against Pharaoh in the usual sense.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.