fire sometimes catch, while other times the flame goes out. The second stanza changes the container to a “censer,” or incense holder. Despite the fullness of that fire, it may go out. Within the ashes, however, the fire remains hidden, awaiting the Lord’s bellows to make the fire of faith glow.

In order to fully understand this metaphor, it is important to know what a tinder box is. A tinder box is a box that contains tinder, which are small fibers or thin slivers of wood that catch fire quickly, as well as a flint and steel. In short, one would use the contents of a tinder box to start a fire rapidly and easily. Thus, when the speaker says that when God first touched them their heart was like God's "tinder box," easily set alight, so to speak, they seem to suggest that the piety they felt as a youth was bright and warm but, ultimately, neither very consistent nor of long duration. This is in contrast with the "censer trim" with which they now compare their heart.

A censer is a container in which one might burn incense during a religious ceremony, perhaps. Incense undergoes a slow burn to release its scent, unlike the quick and fiery burn of tinder. In other words, then, the effect that God has on the speaker now is more subtle but of longer duration than the immediate flame of religious fervor and passion that they would experience as a younger person. This makes their faith, then, appear to be more constant if less showy than it was when they were a youth with a "tinder box" heart. These comparisons show how the speaker's piety and faith have matured throughout their life.