This is a call for all the humans, not just for the Jews who were in Medina; Allah (swt) is addressing His Prophet (saws) and the Muslims to avoid claim sanctity for themselves and their deeds, since any doing whatsoever whether praying, fasting or giving charity would not decrease or increase of Allah’s kingdom in anything. The Prophet (saws) is that among the sayings he relates from his Lord (may He be glorified) is that He said:

“O My servants, you will not attain harming Me so as to harm Me, and will not attain benefitting Me so as to benefit Me. O My servants, were the first of you and the last of you, the human of you and the jinn of you to be as pious as the most pious heart of any one man of you, that would not increase My kingdom in anything. O My servants, were the first of you and the last of you, the human of you and the jinn of you to be as wicked as the most wicked heart of any one man of you, that would not decrease My kingdom in anything.”[1]

As such, we have to do a lot of the deeds that purify us in front of Allah (swt), and not purify ourselves in front of people so that it may be said about us that we did such and such.

( بَلِ اللَّهُ يُزَكِّي مَن يَشَاءُ وَلَا يُظْلَمُونَ فَتِيلًا … ) (…Allah purifies whom He wills, and injustice is not done to them, [even] as much as a thread [inside a date seed]): Allah (swt) treats everyone in absolute justice, never treat unjustly:

 فَمَن يَعْمَلْ مِثْقَالَ ذَرَّةٍ خَيْرًا يَرَهُ % وَمَن يَعْمَلْ مِثْقَالَ ذَرَّةٍ شَرًّا يَرَهُ

(So whoever does an atom’s weight of good will see it, % And whoever does an atom’s weight of evil will see it.) (Az-Zalzalah: 7-8)

[1] Sahih Muslim, The Book of Virtue, Enjoining Good Manners, and Joining of the Ties of Kinship, Chapter: Prohibiting of injustice, Hadith No. 2577.