- Mr 1:7 And preached, saying, There cometh one mightier than I after me, the latchet of whose shoes I am not worthy to stoop down and unloose.
John references the verses that follow Mal 3:1 in describing the one who follows him. He doesn't quote the verses but restates their meaning:
mightier than I
- Mal 3:2 But who may abide the day of his coming? and who shall stand when he appeareth? for he [is] like a refiner’s fire, and like fullers’ soap:
He is mightier: Who can live through the day of his coming?
He is mightier: Who can stand in his presence? "Every knee will bow.." 
He is mightier: He will clean the essence and the outside. 
- Mal 3:3 And he shall sit [as] a refiner and purifier of silver: and he shall purify the sons of Levi, and purge them as gold and silver, that they may offer unto the LORD an offering in righteousness.
The word for latchet comes from the root of 'untwisting'. The shoes were held on by twisting the thong into a knot. John has just quoted the prophecy that he is the one making straight the way of the Lord, but then humbly confesses that he is not even worthy to make straight the thong on his shoe.
Next Mr 1:8
- Php 2:10 That at the name of Jesus every knee should bow, of [things] in heaven, and [things] in earth, and [things] under the earth;
- Isa 1:18 Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.