I know why it snows. So why does the psalm say God sends it?
The second half of this psalm is a weather report with God as the subject of every verb. He covers the sky with clouds, gets rain ready, gives snow like wool, scatters frost like ash, throws ice like crumbs, then sends His word and melts it all. You learned how weather works in elementary school. So is the psalm just old science?
The Rambam (Maimonides, Egypt, 1100s) wrote about this exact verse. In the Guide for the Perplexed, his book on Jewish belief and philosophy, he writes that everything that happens has a nearest cause, and that cause has its own cause, all the way back to the first cause, which is God's will. The prophets, he says, often leave out the causes in the middle and simply say that God did it. His first example is "the melting of the snow when the air warms up," where the verse says: "He sends His word and melts them."
So for the Rambam, "the air got warmer" and "He sent His word" are not two competing explanations. One names the nearest cause. The other names the first one.
The commentators on the psalm read it the same way. Rashi says the wind in that verse is a west wind. Radak says "His word" is the heat of the sun, or rain. Meiri calls all of it "natural things," and says they are still among the most impressive things in nature. Radak explains why the psalm says "His cold": because "nothing is by chance."
Radak also says why you would sing about it. These things happen all the time, to everyone, he writes, and they are God's power and wonders too. Ibn Ezra adds a practical note: a lot of snow in winter is what gives the best wheat in summer.
Not everyone reads these verses as weather. Malbim (Rabbi Meir Leibush Weiser, 1800s) takes the snow and ice as a picture of a harsh decree that freezes everything good, and the melting as that decree being canceled fast. Both readings are in the classic commentaries.
Rambam, Guide for the Perplexed 2:48 (Ibn Tibbon's Hebrew),Rashi, Radak, Ibn Ezra, Meiri and Malbim on Tehillim 147:15-18God doesn't want strength? What is wrong with being strong or fast?
Verse 10 says: "He does not delight in the strength of the horse. He takes no pleasure in a man's legs." In Tanach the horse is a war animal. Rashi reads "legs" as speed, how fast a man can run.
On its own, the line sounds like God has something against strength. Ibn Ezra comes close to that: "God has no desire for strength, only for fear of Him." He connects it to the verses just before. God feeds every creature, he says, and not because of how strong it is. The baby ravens are the witnesses.
Radak and Metzudat David (a commentary on the later books of Tanach, from the 1700s) add one word: trust. God does not want "a person who trusts in the strength of the horse," or who trusts his legs to get him out of the battle. The next verse gives the other side: "Hashem takes pleasure in those who fear Him, in those who wait for His kindness." As they read it, the contrast is about what you count on.
The Ramban (Nachmanides, Spain, 1200s) quotes this verse about soldiers on their way to war. The Torah does not tell them to stay home. They go out and they fight. But they should not think, "We are strong, we are men of war." They should turn their hearts to God and trust in His rescue.
Mishlei has both halves in one line: "The horse is made ready for the day of battle, and victory belongs to Hashem."
Meiri hears encouragement here. The psalm is about a scattered people coming home, and this line tells them not to be scared by the power of the nations, who trust in their horses and their speed.
So is being strong or fast a problem? None of these commentators says so. Ibn Ezra's point is that strength is not what God looks for in a person. The others say the trouble starts when your strength is the thing you rely on. In the psalm just before this one, you said the same about trusting in nobles.
Rashi, Ibn Ezra, Radak, Metzudat David and Meiri on Tehillim 147:10-11,Ramban on Devarim 20:1,Mishlei 21:31,Tehillim 146:3"He did not do this for any other nation." Isn't that arrogant?
The psalm ends: "He tells His words to Yaakov, His decrees and His laws to Israel. He did not do this for any other nation, and those laws they do not know. Halleluyah." It can sound like bragging. The sources read it in more than one way.
Radak reads it as a plain statement about Mount Sinai. He quotes Moshe in Devarim: "Has any people heard the voice of God?" Ibn Ezra says the same: God gave His Torah to His people alone. Metzudat David explains the last word. "For this, praise God." As they read it, the verse states what happened and says thank you.
Did the other nations get nothing? Shemot Rabbah (a Midrash on the book of Shemot) says they got part. Adam was given six commandments, and Noach one more. A king sits at a full table. Each servant who comes in gets one dish. When his son comes in, he gets the whole table. Israel is handed the whole Torah at the moment they say, "We will do and we will listen." In the Gemara, Rabbi Yochanan, a sage in the Land of Israel, says God first took the Torah around to every nation and language, and they did not accept it.
There is a harder side. Rabbi Ami, another sage of the Gemara, learns from this verse that words of Torah are not handed over to a non-Jew. Meiri reads "those laws they do not know" as a judgment: the other nations do not act with fairness or see its worth.
The same Midrash tells of Aquilas, who told the Roman emperor Hadrian that he wanted to become a Jew. Hadrian asked what he saw in a nation that Hadrian himself had shamed and killed. Aquilas answered that the smallest of them knows how God created the world, and that their Torah is true. Hadrian told him to study their Torah without converting. Aquilas said that cannot be done, and quoted this verse.
The sources do say Israel was given something no other nation was. They disagree about how much that shuts others out.
Radak, Ibn Ezra, Metzudat David and Meiri on Tehillim 147:19-20,Devarim 4:33,Shemot Rabbah 30:9 and 30:12,Avodah Zarah 2b,Chagigah 13a