If today you hear his voice, harden not your hearts. “A Call to Praise and Obedience” is how today’s Responsorial Psalm (Psalm 95) is titled (NAB). Twice (vv. 1ff, 6), the Psalmist calls on his hearers to praise and worship the Lord, for the Lord is both king of his creatures (vv. 3-5) and shepherd of his flock (v. 7a-b). In vv. 7c-11, the Psalmist warns his hearers to be faithful to God in order to avoid a repeat of the Israelites’ “contention” with the Lord (putting the Lord to the test) at Massa, an act which which ended up arousing the Lord’s anger (cf. Exodus 17:1-7; Numbers 20:1-11). In their “contention” with the Lord, the Israelites had demonstrated their lack of faith in the Lord their God who had journeyed with them since their flight from Egypt. It was an occurrence that led to the punishment of Moses and Aaron (cf. Numbers 20:12), a situation in which the Psalmist hopes his hearers will not find themselves. All that they need to do, says the Psalmist, is to remain faithful to the Lord by heeding the Lord’s voice.
In the opening verse of the Gospel passage for today, we see the disciples asking Jesus to “increase their faith.” It was a request that did not just “pop” up. It was occasioned. As the disciples marched with Jesus towards Jerusalem, and even as Jesus had revealed to them that it was in Jerusalem that he was destined to undergo his passion, Jesus did not give them a break. He continued to bombard them with teachings on discipleship, that is, on the radical following of him that was expected of them. What they were hearing from Jesus probably scared them since what they were hearing from Jesus sounded undoable if not outright impossible. They were familiar with the Mosaic ‘ eye for an eye’ teaching (cf. Matthew 5:38; Exodus 21:24). They very well knew that one was to be given the same treatment as he/she had shown others (cf. Matthew 7:12). Yet, here was Jesus telling them that the new teaching of the kingdom of God demanded that they surpass the expectation of the old law (cf. Matthew 5:20, 48b). And even if they agreed to give this new teaching a try, forgiving the same person seven times in a day (cf. Luke 17:3b-4) was to ask too much of them. To make matters worse, they were now being told that one could be held responsible for the sin of another. As salt of the earth (cf. Luke 14:34-35) and light to the world, they were now responsible for their souls and the souls of their brothers and sisters (cf. Luke 17:1-3). This was taking the ‘little’ faith they had a little too far. 
In response to the disciples’ request (“Lord, increase our faith”), Jesus reminds them (and us) that there is nothing like ‘little’ or ‘great’ faith. An individual is either a man/woman of faith or he/she is not. Faith is not a commodity that can be quantified (and just in case it can, faith the size of a mustard seed would be enough to do wonders). Faith is not something that is extraneous to an individual. Faith is demonstrated in how an individual lives his/her life (faith is lived). In other words, the disciples needed not to worry about the seeming impossibility of the life required of them, for as a people of faith, impossibility had ceased being an option the moment they said YES to Jesus. As a matter of fact, faith and discipleship are inseparable. By saying YES to Jesus’ summons, a disciple develops a listening ear to his master to the point of becoming his servant. 
Faith is the fuel that keeps discipleship alive. Faith in the master is what keeps a servant focused on, and committed to his/her responsibilities. A faithful servant never sees his/her responsibilities as burdensome but rather as proof of his/her love for the master. What Jesus was asking of the apostles was tough. He was asking them to give more than others since they were going to form the foundation of the Church. He was asking them to be the FAITH upon which the church would be built.