The expression: إِلَىٰ حِينٍ (ila hin: for a time) in: فَآمَنُوا فَمَتَّعْنَاهُمْ إِلَىٰ حِينٍ ([ 147] So, they believed, then, We let them enjoy for a time.- 148) means that as long as they did not revert to their kufr and shirk, no punishment visited them.
Exposing the fraud of the Qadyani imposter
It has already been demonstrated in the Tafsir of Surah Yunus (علیہ السلام) (Ma’ ariful-Qur’ an, English, Volume IV), and it is clear from this verse too, that the reason why the punishment due to visit the people of Sayyidna Yunus (علیہ السلام) was averted was that his people had started believing on time - before it actually materialized. This puts the fraudulent claim of Mirza Ghulam Ahmad Qadiani (the false pretender to prophethood from Qadian located in Punjab, now called Haryana in India) when he had challenged his adversaries that, should they continue to oppose him, it stood decreed that Divine punishment would descend upon them by such and such time. But, quite conversely, the adversaries became stronger and more vocal, yet the punishment never came. At that time, iii order to salvage himself out from the disgrace of failure, the Qadiani imposter started saying that since his adversaries were really scared in their hearts, therefore, this punishment stood removed from them - as it had stood removed from the people of Sayyidna Yunus (علیہ السلام) . But, this verse of the noble Qur'an declares this interpretation to be false and rejected. The reason is that the people of Sayyidna Yunus (علیہ السلام) had stayed safe from the punishment because of their 'iman, belief and faith. Contrary to this was the case of the adversaries of Mirza Ghulam Ahmad of Qadian - not only that they did not believe in him, in fact, their struggle against him gained more strength and momentum.