What are the scholarly sources that mention the multiplication of the reward for good deeds by 700 times during the first ten days of Dhu al-Hijjah, and that fasting each of these days is equivalent to fasting a year?

The source of the saying that deeds are multiplied seven hundredfold in the first ten days of Dhul-Hijjah is a hadith that Al-Albani declared weak. However, the multiplication of good deeds up to seven hundredfold is mentioned in an authentic hadith in Sahih Muslim, and this applies generally to all righteous deeds, not specifically to the first ten days of Dhul-Hijjah.