I marked one passage during my reading.
For some reason, I only knew this passage as it is worded in Matthew.
The first part of each passage is identical. The second half is where they differ. Matthew says that my Father will give me "good things" if I ask. This is how I've always understood this promise. However, Luke says that my Father will give "the Holy Spirit" if I ask. Luke's version is so much more powerful. Good things are always a blessing. But the Holy Spirit being in my life is vitally important. This passage promises that I all I have to do is ask.