Is the phrase "this was not known among the Salaf" a proof and an argument?

The Shaykh : Because it is not a condition for fasting to be in a state of ritual purity, whether from major or minor impurity. As for the prayer that he abandoned and then repented from now, and Allah granted him forgiveness, repentance nullifies what came before it, and praise be to Allah.

The questioner : Your Eminence the Shaykh! We often hear our scholars say, "This was not known among the Salaf." Is this phrase a proof and an argument? I ask for clarification on this.

The Shaykh : Yes, if this matter is from the acts of worship, then if it was not known among the Salaf, it is a bid'ah (religious innovation). Because the Salaf are more knowledgeable than us about the Shari'ah of Allah, more obedient to Allah than us, and more intense than us in obedience. But if it is from the ordinary matters, then it does not harm if it was not customary among the Salaf, because customs differ according to the difference in time and place. This is the criterion.