I believe this is the full quote:
So, then, brethren, having received no small occasion to repent, while we have opportunity, let us turn to God who called us, while yet we have One to receive us. For if we renounce these indulgences and conquer the soul by not fulfilling its wicked desires, we shall be partakers of the mercy of Jesus. Know that the day of judgment draws near like a burning oven, and certain of the heavens and all the earth will melt, like lead melting in fire; and then will appear the hidden and manifest deeds of men. Good, then, is alms as repentance from sin; better is fasting than prayer, and alms than both; "charity covers a multitude of sins", and prayer out of a good conscience delivers from death. Blessed is every one that shall be found complete in these; for alms lightens the burden of sin.
2nd letter of Clement to the Cornthians
In the letter, "charity covers a multitude of sins" is quoted and that is a reference to the first letter of St. Peter
Charity covers a multitude of sins
1 Peter 4:4
There's a similar passage in Sirach that goes
Store up almsgiving in your treasury, and it will save you from every evil.
But, even though Ben Sirach was seemingly referring to temporal salvation (i.e. in time of distress or need), there's a clear anagogical reading of that which echos Jesus saying to store up your treasures in Heaven where neither moth nor worm can eat them.
There's an even clearer mandate in the Book of Tobit
For alms delivereth from death, and the same is that which purgeth away sins, and maketh to find mercy and life everlasting.
Combined, it doesn't make the quote from Clements letter (which is a spurious attribution, according to New Advent), contrary to scripture. It is interesting that both of the scripture passages I quoth are deuterocanonical, and maybe all the more interesting if you came from a Sola Fide background and were thinking that Clement was off his rocker because you never saw this kind of talk in your Bible.
That fasting is better than prayer, should be no surprise, when the disciples attempts to drive out demons failed Jesus said
He said to them, "This kind can only come out through prayer."
Mark 9:29 NAB
Well what were they doing? So some manuscripts also tack on "And fasting" (without saying who is doing the fasting)
Anyway, it's semi-clear that fasting + prayer is better than prayer alone. And in a way, almsgiving is better than both. But it's the combination of them that sets you on the right path.