Other comments on this day's readings can be found here.
Reading 1 - 1Samuel 31:9,10
"They cut off his [Saul's] head and stripped off his armor, and they sent messengers throughout the land of the Philistines to proclaim the news in the temple of their idols and among their people. They put his armor in the temple of the Ashtoreths and fastened his body to the wall of Beth Shan" (1Sa 31:9,10).
The death of Saul was very similar to, and reminiscent of, the death of Goliath: 1Sa 17:54; 21:9.
And so this fulfilled the words of David, in the Psalms: "God scattered the bones of those who attacked you; you put them to shame, for God despised them" (Psa 53:5).
Reading 2 - Jeremiah 6:16
"This is what the LORD says: 'Stand at the crossroads and look; ask for the ancient paths, ask where the good way is, and walk in it, and you will find rest for your souls' " (Jer 6:16).
More familiarly, the AV has "the old paths". This refers to the clear, well-marked, well-trodden paths, devoid of pitfalls or precipices -- in which the careful shepherd might lead his flock.
"Rest for your souls" was appropriated by the Lord Jesus in his great invitation: "Come to me, all you who are weary and burdened, and I will give you rest. Take my yoke upon you and learn from me, for I am gentle and humble in heart, and you will find rest for your souls. For my yoke is easy and my burden is light" (Mat 11:28-30).
"Never was appeal more powerfully made, more superbly translated into words of one syllable, than in the warm humanity of Jeremiah's words, which were one day to become a model for the Son of God when he in his turn laid siege to the wilful hearts of Israel... Stand! see! ask! and ye shall find! Even their walking in the old paths was itself to prove a refreshing rest from their present jading life of vanity" (Harry Whittaker, "Jeremiah" 42).
Reading 3 - Matthew 17:20
"Because you have so little faith. I tell you the truth, if you have faith as small as a mustard seed, you can say to this mountain, 'Move from here to there' and it will move. Nothing will be impossible for you" (Mat 17:20).
If nothing will be impossible, then it is implied that all things will be possible.
Here, I think, the "all things" needs to be limited to "all things which are in accordance with the will of the Father", or "all things which are for your ultimate benefit". We are like little children; if we somehow were given 'carte blanche' to have anything and everything WE want, then there would be no end to the damage we could do to ourselves and others. We need to be protected from ourselves. A loving Father would never give us the keys to the "candy store", and then leave us alone to gorge ourselves.
But... "all things" which work together for our ultimate salvation? Yes, of course, He will give us that. Consider Rom 8: "If God is for us, who can be against us? He who did not spare his own Son, but gave him up for us all -- how will he not also, along with him, graciously give us ALL THINGS? Who will bring any charge against those whom God has chosen? It is God who justifies. Who is he that condemns? Christ Jesus, who died -- more than that, who was raised to life -- is at the right hand of God and is also interceding for us. Who shall separate us from the love of Christ? Shall trouble or hardship or persecution or famine or nakedness or danger or sword... No, in all these things we are more than conquerors through him who loved us. For I am convinced that neither death nor life, neither angels nor demons, neither the present nor the future, nor any powers, neither height nor depth, nor anything else in all creation, will be able to separate us from the love of God that is in Christ Jesus our Lord."
This passage puts the same point both positively and negatively: firstly, God will give us "all things" that will help us, to the utmost of His power, to attain to lasting faith, true forgiveness of sins, and a place in His kingdom. And thus we are assured that "nothing" (not even death itself, or terrible persecutions or trials) will keep us from the love of God in Christ, and a place in that Kingdom.
Having said that, I might add -- yes, in fact, even the greatest "mountain" will be moved, if we ask it. First of all, the asking ought to be in keeping with the will of God. And secondly, Jesus didn't state limitations as to TIME! One day, when Christ returns, the whole world will be "torn down" and "rebuilt" in a new and glorious "creation", and every "mountain" (all the kingdoms, creations, wealth, and power of sinful man) will be brought low! It WILL happen. And we will be there to see it if we have faith as a grain of mustard seed, and if we pray for that day to come.
I'm looking forward to seeing all the "mountains" moved (Rev 6:14)! Maybe I'll move a few myself... if Christ asks me to do so!
Is it possible that the greatest "mountain" is (and was) the "great stone" which sealed shut the tomb of Jesus (Mat 28:2-4; Mar 16:4; Luk 24:2; Joh 20:1)? And this mountain has already been moved!